Mysterious necrotic spots

[RuggedWombat]

I was hoping somebody could finally tell me what is happening with these brown necrotic spots on the leaves. I've been dealing with this issue in some form since atleast May 2022, and no matter how good the plants are doing, this issue seems to keep popping up and its driving me insane.

The basics about the grow are:
Promix HP
5 gallon plastic nursery pots
PH 6.3-6.5
Feeding is 100% of DG feed chart with no fresh water feedings in between nutrients
light is SF G4500
Temp- min 66.2- max 81.7 avg 73 F.
RH avg- 64.3%
Dynagro Foliage Pro, Mag Pro, and Protekt

So far my leading theories are calcium (brown speckles) and perhaps magnesium) interveinal chlorosis. Cannabis has a harder time absorbing cal and mag below 6.5 so thats my top theory.
A second theory is perhaps moisture stress. Not exactly over or underwatering, but just the plants leaves always seem papery even when being watered frequently so perhaps the medium itself is having issues and the moisture is being drawn from the leaves to balance it out? Whats confusing is the plants overall look VERY nice. Very green throughout with lots of new healthy grow. Thats what makes these continuing mystery symptoms so frustrating. Here are some pictures going back as far as May of last year until the present. They are posted from the present to the past.

Grow 11

 

[RuggedWombat]

I was hoping somebody could finally tell me what is happening with these brown necrotic spots on the leaves. I've been dealing with this issue in some form since atleast May 2022, and no matter how good the plants are doing, this issue seems to keep popping up and its driving me insane.

The basics about the grow are:
Promix HP
5 gallon plastic nursery pots
PH 6.3-6.5
Feeding is 100% of DG feed chart with no fresh water feedings in between nutrients
light is SF G4500
Temp- min 66.2- max 81.7 avg 73 F.
RH avg- 64.3%
Dynagro Foliage Pro, Mag Pro, and Protekt

So far my leading theories are calcium (brown speckles) and perhaps magnesium) interveinal chlorosis. Cannabis has a harder time absorbing cal and mag below 6.5 so thats my top theory.
A second theory is perhaps moisture stress. Not exactly over or underwatering, but just the plants leaves always seem papery even when being watered frequently so perhaps the medium itself is having issues and the moisture is being drawn from the leaves to balance it out? Whats confusing is the plants overall look VERY nice. Very green throughout with lots of new healthy grow. Thats what makes these continuing mystery symptoms so frustrating. Here are some pictures going back as far as May of last year until the present. They are posted from the present to the past.

Grow 11

 

[RuggedWombat]

Grow 10

 

[RuggedWombat]

Grow 9

 

[RuggedWombat]

Grow 8

 

[RuggedWombat]

Grow 7

 

[RuggedWombat]

Grow 11

 

[DancesWithWeeds]

It sounds to me like you are doing the same thing every time and expecting different results. Are you on the west coast? And did you start from seed or clone? I've seen pictures of HLV (hop latent virus) that look look something like that.

 

[RuggedWombat]

It sounds to me like you are doing the same thing every time and expecting different results. Are you on the west coast? And did you start from seed or clone? I've seen pictures of HLV (hop latent virus) that look look something like that.

East Coast and started from seed. I think the only variable worth changing right now is vary the PH a bit and see if it helps. I mean cal/mag absorption starts struggling around the range Im in which would match some of the spotted leaves symptoms. It's more the necrotic brown spots between the veins I'm curious about.

 

[warble]

I am going to say salt build up. PPMs too high. I mean just look at how dark green those healthy leaves are. Way too much nitrogen. 6.5? Maybe drop that a few points too. Impressed that there is very little tip burn from the pics. Overall you could be doing worse. I'm sure once you dial in the feeding and get plenty of runoff they'll take off. Keep up the good work.

 

[RuggedWombat]

I am going to say salt build up. PPMs too high. I mean just look at how dark green those healthy leaves are. Way too much nitrogen. 6.5? Maybe drop that a few points too. Impressed that there is very little tip burn from the pics. Overall you could be doing worse. I'm sure once you dial in the feeding and get plenty of runoff they'll take off. Keep up the good work.

I figured the medium was already too acidic and that's where the brown speckling was coming from due to lack of calcium. I think the salt build up definitely contributes to the brown necrotic spots between the veins however. I was thinking doing 75% of the feed schedule instead of 100% and maybe try a feed at like 6.6-6.7? I mean the super speckled leaves don't look like calcium to you? They've been getting around 800-900 PPM which doesn't seem that excessive in veg but I definitely see signs of some nutrient burn.

 

[warble]

I'd drop the Ph to 5.8 or even lower to get the salts out. I've never fed veg plants more than 600ppm. Your mileage may vary. I don't grow trees, just bushes. Does look like cal def, but could also be caused by root rot. Have you tried to let them dry a while longer between feedings? I wait until the leaves droop before I feed. You don't have to go that far.

 

[RuggedWombat]

I'd drop the Ph to 5.8 or even lower to get the salts out. I've never fed veg plants more than 600ppm. Your mileage may vary. I don't grow trees, just bushes. Does look like cal def, but could also be caused by root rot. Have you tried to let them dry a while longer between feedings? I wait until the leaves droop before I feed. You don't have to go that far.

Well problem is Promix can't get too dry or it is even more difficult to get wet again. Also watering after it's too dry can make the moisture issues worse. How would lowering the PH help with salt removal? I agree with lowering the PPM, would if it's struggling to absorb calcium at the top end of the range then putting way deeper into the red is going to hurt absorption even more correct?

 

[warble]

I use promix too, but when it gets too dry I just take my time feeding. I mist the top of the soil then pour some nutes. Let that absorb and pour some more, again and again until I get some runoff. When I'm getting runoff, I pour a bunch more and have that drain to waste. After the pot stops dripping I pour a bunch more and the let that drain and put it back in it's position in the tent. Runoff should get rid of salts in your high Ph soil. Ph and PPMs will go from high to lower concentrations and then go out with your runoff. Please correct me if I'm wrong.
If you want you could add some aloe powder (helps peat absorb moisture) to your nutes. I've done it, when I was in a hurry. I don't recommend it. It works by the next time you hydrate, the resistance is increased. Be careful, you could get dry zones. I got that problem with my pineapple plant, so now I dunk it. Could be a problem when it gets bigger.

 

[LeastExpectedGrower]

Yeah, I'd bundle much of these posts together.

Promix HP: Adjust your pH downward to 5.7-6.1 range (I aim at 5.8 ). I've never used Dyna-Gro but even with other nutrients I don't usually exceed about 1.8EC (~900ppm).

I'd push maybe twice as much water through that medium to try to fully saturate it but also remove a bunch of the old nutrients. Then I'd keep an eye on the feeding schedule so your soil doesn't dry to far back. For me in Promix HP/5g bags that's generally every 2 days or every-other day depending on the plant, size & time of cycle, and I feed every time (no straight watering) . I generally aim at 25% runoff to get rid of any old nutrients as well.

The drier the Promix gets, it throws pH off and screws w/ uptake as well as depositing dry salts in the medium and becoming hydrophobic.



^^^ this is 5g of Maxibloom, and you can see a little tip-burn so probably could do with 4.5g really. They look dark but that's because I hit them with a good amount of Mg at the beginning of flower, not a nitrogen thing. I also use 2ml of Ca/Mg per gallon as well.

 

[Billy the Mountain]

I figured the medium was already too acidic and that's where the brown speckling was coming from due to lack of calcium. I think the salt build up definitely contributes to the brown necrotic spots between the veins however. I was thinking doing 75% of the feed schedule instead of 100% and maybe try a feed at like 6.6-6.7? I mean the super speckled leaves don't look like calcium to you? They've been getting around 800-900 PPM which doesn't seem that excessive in veg but I definitely see signs of some nutrient burn.

It probably is a calcium deficiency but raising the pH is not a solution.
I think the root cause is the fact that DynaGro has minimal calcium, only 2% iirc.
Maxi Gro has 6% Ca, MegaCrop 7.5% for comparison.

Also, at 10ml/G of Foilage Pro, you're giving > 300!! ppm of Nitrogen, that's ridiculously high.
10ml FPro + 5ml ProTekt + 2.5 ml MagPro per gallon will result in an EC near 3.0, also way too high.

Nutrient profile of the above mix:

 

[StoneDHedgE]

Too salty.

 

[RuggedWombat]

Yeah, I'd bundle much of these posts together.

Promix HP: Adjust your pH downward to 5.7-6.1 range (I aim at 5.. I've never used Dyna-Gro but even with other nutrients I don't usually exceed about 1.8EC (~900ppm).

I'd push maybe twice as much water through that medium to try to fully saturate it but also remove a bunch of the old nutrients. Then I'd keep an eye on the feeding schedule so your soil doesn't dry to far back. For me in Promix HP/5g bags that's generally every 2 days or every-other day depending on the plant, size & time of cycle, and I feed every time (no straight watering) . I generally aim at 25% runoff to get rid of any old nutrients as well.

The drier the Promix gets, it throws pH off and screws w/ uptake as well as depositing dry salts in the medium and becoming hydrophobic.

View attachment 5346717

^^^ this is 5g of Maxibloom, and you can see a little tip-burn so probably could do with 4.5g really. They look dark but that's because I hit them with a good amount of Mg at the beginning of flower, not a nitrogen thing. I also use 2ml of Ca/Mg per gallon as well.

I'm not so sure it is a ph issue though. I ran 6.3-6.5 PH Promix for 2 grows straight and even though they had issues for awhile, they finished with outstanding results. If anything doing feed water feed probably caused more issues as that means they went around a week between feedings when I watered every 3 days.

I will say though moisture stress seems likely. I did a fresh water feed and then a light feeding around 400 PPM and they seem to be bouncing back, especially new growth. Though I KNOW there is a mag issue after starving them a bit. Just look at that interveinal chlorosis. My plan going forward is to water more frequently and cap the amount of foliage pro at 1/2 tsp per gallon. If the plants start to show deficiencies now that they are in flower, I can add a tiny bit of mag pro.

11/24 F8
3 gal water
1/4 tsp PT per gallon
1/4 tsp FP per gallon
1/8 tsp MP per gallon
6 PH
370 PPM

11/27 F11
3 gal water
1/8 tsp PT per gallon
1/2 tsp FP per gallon
1/8 tsp per gallon
6.3 PH
830 PPM

 

[RuggedWombat]

It probably is a calcium deficiency but raising the pH is not a solution.
I think the root cause is the fact that DynaGro has minimal calcium, only 2% iirc.
Maxi Gro has 6% Ca, MegaCrop 7.5% for comparison.

Also, at 10ml/G of Foilage Pro, you're giving > 300!! ppm of Nitrogen, that's ridiculously high.
10ml FPro + 5ml ProTekt + 2.5 ml MagPro per gallon will result in an EC near 3.0, also way too high.

Nutrient profile of the above mix:
View attachment 5346738

Is this a tool you can just plug and play hypothetical numbers? Also the foliage pro calcium debate is impossible to figure out as it's been going back and forth on these forums for years now. Every person who says it doesn't have enough calcium is met with pictures of perfect plants who disagree. I've seen plenty of people who used nothing but foliage pro from start to finish with amazing results and 0 calcium issues. I've seen plenty of others who swear they had nothing but brown spots with just foliage pro so I really have no clue at this point. Just like PH in Promix. One school says 6.1-6.5 and another says like 5.5-5.9 and yet both still seem to work. I mean I'm competent enough to get great results, but it continues to get frustrating that I can't seem to ever be truly issue free...always something.

 

[StoneDHedgE]

Imho....you're feeding too much. Try not to make it complicated. Carry on with what you were doing. But don't feed full strength, back it off to 75% or less or something. See how that goes. Remember every plant/strain different.