Buds not fattening please diagnose leaf colour

Hello all, growing RDWC, just into 7th week with a 9-10 week strain. Feeding at 1.6 (background 0.2) PH 5.7. Room humidity is quite low mid twenties mid thirties lights on fifties lights off. I did have PH problems dropping but sorted it out quite quickly. 6oow HPS 18 inch above canopy.

The buds are just not fattening, fan leaves are dry and a little brittle and look terrible. Any ideas?

Mr Blue,
Just noticed nobody responded. I have a few opinions...but it's almost too late to do anything.

You have to raise your RH. It's not an option.

The burning on the leaf adge could be nutrient burn and running 1.6 ec...that could be the case. I'd drop nute level...make sure you have appropriate calmag amounts and ride it out. I'd hesitate adding any kind of booster at this point. Hopefully others will have an opinion...
JD

fartoblue said:

Room humidity is quite low mid twenties mid thirties lights on fifties lights off.

Click to expand...

fartoblue said:

6oow HPS 18 inch above canopy.

Click to expand...

fartoblue said:

fan leaves are dry and a little brittle and look terrible. Any ideas?

Click to expand...

You pretty much answered your own question. What are your temps? The humidity is way too low..plants are forced to close their stomata and pretty much shutdown.

Yeah, I would certainly drop your nutrients..being that close to being done, your plant's appetite will (or already has) begin to taper off. As JohnDee and Blitz stated, raise your humidity. You'd be really surprised at the kind of leaf symptoms that occur from humidity stress. Us hydro growers tend to forget about humidity sometimes lol.

Looks like cal/mag deficiency to me but i dont grow in dwc, but except for the leaf edges thats what cal/mag def looks like in my garden. With 3 weeks to go i would really think twice about lowering your nutes to much. The last 3 to 4 weeks is when the weight puts on.

It can't put on any weight in the shape it is in right now. Need to get it healthy again, then if you want to push up the PPM's you can.

I think a pic of the plant would help!

Bigworm4201982 said:

Looks like cal/mag deficiency to me but i dont grow in dwc, but except for the leaf edges thats what cal/mag def looks like in my garden. With 3 weeks to go i would really think twice about lowering your nutes to much. The last 3 to 4 weeks is when the weight puts on.

Click to expand...

So which is it Ca or Mg?

Both don’t appear together.

An abundance of one can cause symptoms of the other.

Here’s a tip.

Red dots leading to white dots leading to over all burnt looking leaves is Ca.

Pale yellow interveinal, leading to burnt edges and tips = Mg.


The big question is what’s causing it.


Starting water could be low on Mg.

Nutrients could be low on Mg.

Source water could be high in Ca causing Mg deficiency symptoms.

My advice.

Post a whole plant pic,

post details of water and Ca and Mg levels of nutrients.

Simplest advice is drop EC to around 1.2 and pH around 6. Yes a little high for hydro but makes Mg more available to the plant.

Looks like light burn to me.

Yeah I think a full plant picture would really help us help you on this one.

Many thanks for all of your replies. Dropped the ec to 1.2 and ph to 6 but they drank very little if anything for 2 days and PH dropped again so I presume they have locked out. I decided to drain the full system and just refill with PH water. EC is now around 0.5, my tap water is 0,2 but I can't get into the tubs to drain the bottom out. Thinking of leaving them for 18 hours or so and checking if they have started to drink then will up feed to around 1.0 for a week then drain again and just put them on a finishing feed for 7 days before flush.

The finishing feed requires no other nutrients (Dragon Force by Shogun) Should I feed this at their full recommended dose? Not sure if I can post a link to the product so won't chance my luck.

Once again many thanks for all of the replies very kind of you to take the time.

I will post a picture of the full plants tomorrow.

JohnDee said:

Mr Blue,
Just noticed nobody responded. I have a few opinions...but it's almost too late to do anything.

You have to raise your RH. It's not an option.

The burning on the leaf adge could be nutrient burn and running 1.6 ec...that could be the case. I'd drop nute level...make sure you have appropriate calmag amounts and ride it out. I'd hesitate adding any kind of booster at this point. Hopefully others will have an opinion...
JD

Click to expand...

Looks quite a bit like heat stress to me, personally. Not only is the RH too low but OP has his lights a mere 18 inches away from the canopy. Unless his hood is vented then that is way too close to the canopy, especially with low RH.

Something else I discovered the hard way is that water could be causing Ca/Mg issues. I don't know about the OPs water, but personally my water has loads of Calcium in it. The Calcium in my water, combined with the calcium in my soil lead to calcium salt build up which ended up locking out Magnesium for me. That could be something for the OP to look into as well, but the way those leaves look combined with the light being too close and the RH never being above 30% leads me to believe it's heat stress.

OP, go sit in your tent underneath the light for a few minutes and see how long you can handle it. Your poor plants are probably just too hot.

On another note, breeder times are typically just rough estimates. Use that to your advantage, raise your light and RH as soon as possible. The last couple of weeks is when the buds really start to swell up. While your yields are definitely going to suffer a bit because of this, you can still mitigate some of the damage if you act quickly.

Looks like a potassium deficiency probably. Could be heat though, eliminate that first.

Renfro said:

Looks like a potassium deficiency probably. Could be heat though, eliminate that first.

Click to expand...

These were my 2 thoughts. But a full plant picture would help. If it was heat, the tops would be affected the most.

Or potasium/mag.



Whats your nutrient formula? numbers? brands?

Your girl is short on Mg and probably has been for a while. At this point in the game, I wouldn't go trying to force feed it Mg...it is what it is. I would simply review my past feed notes and make notes for the future to avoid the problem again.

Your RH is a bit low too. Try and bring it up.

As to your light height...I doubt it's your issue, but...hold the top of your hand at the top of your plant canopy, directly under your light...if your hand gets excessively warm, then your plant surfaces most likely feel the same way...if your hand is comfortable, most likely your plant is too. This is something you'll have to determine on your own.

Long story short, do what you must to get her to the finish line...good luck.