Possible Heat Stress?

[Greenshark]

I'm on day 16 of flower.

12 plants
8 600w hps
In In England and we are having a heat wave at the moment. I'm running the lights through the night. The day time temp ( their sleep time ) is getting silly ( 30-31c. Their lights on temp ranges from 26-28.5 so it's warmer when they're sleeping than when they're awake....

Humidity is 45 percent.
Growing in coco in 10 gallon rhizzo pots.
Feeding every day @ 9 litres @ 1.4 ec.

The last 4 days the new leaves coming out of the buds seem to be like an upside down canoe. I've taken the best photos I can. The leaves that are affected feel dry. I thought it might be wind burn so I've turned my fans down and due to the heat they had pure water for 4 days. It doesn't appear to be on all the leaves.

Any help would be greatly appreciated.

 

[JWM2]

Kinda sounds like nitrogen toxicity. Too much nitrogen in your grow medium.

 

[Jack og]

Kinda sounds like nitrogen toxicity. Too much nitrogen in your grow medium.

Have to agree with you , maybe a good flush is in order. Also what’s the lights out temp and humidity like?
I’ve found that if my lights on Vs lights off temps stay constant with leftover nitrogen I get the same effect.
Usually a flush and lowering temps bounces them back. Also check the ph on runoff. See if there is a lockout happening

 

[Greenshark]

Kinda sounds like nitrogen toxicity. Too much nitrogen in your grow medium.

The reason for the straight water for 4 days was because I suspected I had N toxicity and I didn't want to flush in flower really. The leaves had started to claw and they were very dark green. They deffo look better after 4 days of water but the new leaves ( not all of them which is odd ) are being affected still. It looks like wind damage. The temp has been silly lately and I know heat can bring about N toxicity or help with it. Pain in the ass it's happened as I have flipped them!

 

[Greenshark]

Have to agree with you , maybe a good flush is in order. Also what’s the lights out temp and humidity like?
I’ve found that if my lights on Vs lights off temps stay constant with leftover nitrogen I get the same effect.
Usually a flush and lowering temps bounces them back. Also check the ph on runoff. See if there is a lockout happening

Lights off temp is between 27-31 and lights on temp is between 25-29 so it's probably confusing them. Would this bring about N toxicity?

 

[Jack og]

Lights off temp is between 27-31 and lights on temp is between 25-29 so it's probably confusing them. Would this bring about N toxicity?

Yes. It would

 

[Greenshark]

Have to agree with you , maybe a good flush is in order. Also what’s the lights out temp and humidity like?
I’ve found that if my lights on Vs lights off temps stay constant with leftover nitrogen I get the same effect.
Usually a flush and lowering temps bounces them back. Also check the ph on runoff. See if there is a lockout happening

Just checked the run off, it was 1300 ppm which is far too high. They had straight water for 4 days so god knows what it was before. The ph was 5.68 which isn't too bad but what has caused the lockouts? Would N toxicity cause a lockout?

 

[Greenshark]

It's only on some of the new leaves as well?

 

[Jack og]

Just checked the run off, it was 1300 ppm which is far too high. They had straight water for 4 days so god knows what it was before. The ph was 5.68 which isn't too bad but what has caused the lockouts? Would N toxicity cause a lockout?

Higher ph combined with high ppm tends to cause lockout, I’d monitor the run off next few water cycle. Let them dry then water with higher runoff, do this a few times , and then start with cal mag, micro feed. Cut nutes to a third until new growth looks robust. I think the worst maybe behind ya. She will bounce back once the nutes are used up.

 

[Greenshark]

Higher ph combined with high ppm tends to cause lockout, I’d monitor the run off next few water cycle. Let them dry then water with higher runoff, do this a few times , and then start with cal mag, micro feed. Cut nutes to a third until new growth looks robust. I think the worst maybe behind ya. She will bounce back once the nutes are used up.

I'm 19 days in to flower now so I can't use cal mag as it contains nitrogen. I also can't let the pots dry out as I'm using coco.... it will just make my problem worse. I'm confused as to why they're locked out. I never go above 800-850 ppm and it looks more like an N toxicity. Will too much N in coco cause a lockout?

 

[Greenshark]

I'm thinking the heat wave has shocked them as they started using less water so I reckon that's what has caused the lockout.

 

[Jack og]

You can water more and feed less and see if she bounces back, cal mag has negligible amounts of nitrogen, helps feed at micro level so I wouldn’t worry too much, part of our regiment is cal mag into flower, just not to late into it. In coco, the plants use em up so fast it wouldn’t hurt the flower stage

 

[Greenshark]

You can water more and feed less and see if she bounces back, cal mag has negligible amounts of nitrogen, helps feed at micro level so I wouldn’t worry too much, part of our regiment is cal mag into flower, just not to late into it. In coco, the plants use em up so fast it wouldn’t hurt the flower stage

They were locked out mate. All sorted now. 750ppm going in and 750ppm coming out with a ph of 5.85 :)

Thanks for your help

 

[houseofgas]

They were locked out mate. All sorted now. 750ppm going in and 750ppm coming out with a ph of 5.85 :)

Thanks for your help

Did you figure out the root cause of your problem? I’m having similar issue