Can't figure this out

I am growing dwc and as the pictures show I have yellowing leaves with rust colored spots. Initially I thought it might be the beginning of light burn as it is only on a few leaves at the top of plant. So I raised the light. That didn't help. So then I thought maybe it was a calmag issue so I upped the calmag to 3 ml per gallon. That doesn't seem to have worked. So I thought I would ask you guys. I am running a Growers Choice roi 420 for lighting. Air temp is 81 degrees and humidity is pretty steady at around 50 percent. My water temp stays steady at 68 degrees. I keep my ec at 1.4 to 1.6. I run gh nutes and and change reservoir every week. I do use tap water and my par readings are at 851. I am also on day 24 since I flipped. I hope I gave you guys enough info to help me. Thanks in advance for any help.

AS it's only on a few of those top leaves it likely is/was an issue with the light placement unless it's getting worse and spreading down the plant.

Ones lower down at the top of colas don't look affected so it's not likely a deficiency of any kind.

The pics are pretty washed out so hard to see the affected ones clearly. Try a shot with the flash just after lights out.

R

OldMedUser said:

AS it's only on a few of those top leaves it likely is/was an issue with the light placement unless it's getting worse and spreading down the plant.

Ones lower down at the top of colas don't look affected so it's not likely a deficiency of any kind.

The pics are pretty washed out so hard to see the affected ones clearly. Try a shot with the flash just after lights out.

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Thanks for the reply. I will take better pic. Lights go out in about 30 minutes.

Here is better pics. I also forgot to add that I keep ph between 6.2 and 6.4 and that the strain is super skunk.

Have you scoped for bugs?

This leaf in particular scares me

Johiem said:

Have you scoped for bugs?

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Yes I have scoped for bugs. All I have found is the occasional fungus gnat. But I have treated for them and they are dying off. Thanks for the reply

Johiem said:

This leaf in particular scares me

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That happened when my wife was taking care of plant for me and she says she accidentally touched the light with the plant.

That's way better. I can see very mild nute burn on the tips of leaves so it's quite possible the heat from the lights were causing the upper leaves to draw up more water to keep cool, (it's a real thing), and pulling in more nutes with it causing some local toxic salts buildup. You see how the points along the edges of those affected leaves are also burnt a bit but unaffected leaves aren't? Shows there's more nutes in the bad leaves causing that.

Now that you've moved the light up keep a close eye on the burnt leaves and see if they get worse. They quite likely will but if other leaves aren't showing it then it's not a big deal.

Really dark leaves so I would back off on the nutes or you will likely see all the big leaves start going like that but a lot worse about mid-flower as toxic salts buildup really gets going. I've had a lot of problems with that and turned out with my really low RH they were storing all the extra nutes in the leaves until they just start to fry in the middle of budding. So when my RH is lower like now I'm feeding at half my usual dose which is half the max on the bottles.

You haven't sprayed with anything have you?

Overall they look great and if the problem doesn't expand then should be good to go but I would drop your ppm to 500 from the 700 - 800 it's at now. And are you giving equal amounts of each nute assuming your GH is the 3-part? I feed Lucas Formula style after the stretch to reduce the N by dropping the Grow and using half as much Micro as Bloom. Some Epsom Salts will give them the extra Mg they like at this stage and S to help with resin production. Too much P after the stretch isn't good but they like a little extra K then too. I use Big Bud powder a week before flipping to 12/12 and for the first few weeks but at half or less than recommended. I will use more Bloom so don't need tons of BB.

Keep a close eye and if it's as I think then it shouldn't get much worse before it gets better. Those leaves will never get better but hopefully not worse.

Skillcraft said:

That happened when my wife was taking care of plant for me and she says she accidentally touched the light with the plant.

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I worked out of town in bush camps a lot and my wife let a rouge male pollinate a room full of plants while I was gone for a month. She was watering it and wondering why it was different than the rest. lol Then a year later while I was on a 2 month job mites took over. Wiped out everything including a mother I'd had for 5 years. Looked like an old horror movie set with cobwebs covering every plant like a gossamer tarp thrown over them.

Can't kill 'em so you gotta love 'em.

No I have not sprayed with anything. I will try dropping ec tomorrow. I will clean res and drop strength of nutes. Yes I am using 3 part gh nutes. I have not stopped the grow nutes. I add 3 mils per gallon in flower. But I do add equal part of micro and bloom. Just curious could I be using to much bloom.?

Skillcraft said:

No I have not sprayed with anything. I will try dropping ec tomorrow. I will clean res and drop strength of nutes. Yes I am using 3 part gh nutes. I have not stopped the grow nutes. I add 3 mils per gallon in flower. But I do add equal part of micro and bloom. Just curious could I be using to much bloom.?

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If you look up Lucas Formula they say to use 4ml Micro and 8ml Bloom but you mix in that ratio, (0-1-2), using how many mls of each that will get you 500ppm of actual nutes. So start with say 2ml Micro and 4mls Bloom in a gal and test the ppm. Actually you should check the ppm of your water then add the Micro and check then add the Bloom. From that you can calculate how much to add to reach any ppm level you want. Micro raises the ppm much more than the other two. Got a lot of N and the bulk of the micronutrients that also add to the number.

The Lucas Formula has been used for ages by a lot of growers and some use it from start to finish with great results but I always found it a bit low on N when doing DWC and the plants were growing so fast in veg. Also I believe a lot of the Mg is in the Grow so you want some Epsom Salts to cover that loss. 2tsp/gal is good. 4 if treating a deficiency.

OldMedUser said:

If you look up Lucas Formula they say to use 4ml Micro and 8ml Bloom but you mix in that ratio, (0-1-2), using how many mls of each that will get you 500ppm of actual nutes. So start with say 2ml Micro and 4mls Bloom in a gal and test the ppm. Actually you should check the ppm of your water then add the Micro and check then add the Bloom. From that you can calculate how much to add to reach any ppm level you want. Micro raises the ppm much more than the other two. Got a lot of N and the bulk of the micronutrients that also add to the number.

The Lucas Formula has been used for ages by a lot of growers and some use it from start to finish with great results but I always found it a bit low on N when doing DWC and the plants were growing so fast in veg. Also I believe a lot of the Mg is in the Grow so you want some Epsom Salts to cover that loss. 2tsp/gal is good. 4 if treating a deficiency.

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Ok. I will take your advice and do that tomorrow morning. Thank you so much for taking the time to answer my questions. Happy New Year and happy growing.

Skillcraft said:

Ok. I will take your advice and do that tomorrow morning. Thank you so much for taking the time to answer my questions. Happy New Year and happy growing.

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U2!

OldMedUser said:

U2!

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He said he’s doing DWC and keeps his PH at 6.2-6.4. Doesn’t that seem like the higher end and maybe dropped to 5.8-5.9 to see if that helps at all?

Incredible4Mr2E said:

He said he’s doing DWC and keeps his PH at 6.2-6.4. Doesn’t that seem like the higher end and maybe dropped to 5.8-5.9 to see if that helps at all?

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I didn't see that one line at the top of the pics abot pH but yeah I'd aim lower on the pH tho it's not really out of range much if at all. On my top ups every 3 days using the older style AN nutes without pH Perfect it would be up to 6.2 - 6.4 and I'd knock it back with 4 or 5 drops of conc. sulphuric acid to sometimes as low as 5.2 then 3 days later it was back up. I wasn't checking between top ups so it could have gone up right away and I didn't notice.

I certainly don't see any issues with the very top leaves which is where badly out of range pH is most likely to show as it tends to block some micronutrients which will show in newer growth first. The macro nutrients are very available at almost any pH unless it's wildly out of range.

So @Skillcraft if you've been running them at that pH all along then I wouldn't worry about it as for the most part everything's fine. One other thing I thought those spots could be is leaf sepotoria which is a fungal thing and shows the necrotic spots in the centres but it likes damp areas to start up and those affected leaves are in an area that is the least likely to be damp. Being anal about keeping a specific pH and using lots of pH up or down can cause more problems than it fixes.