Leaf Burn When Switching To Flower

[diogodasilva]

Hey guys˜!
This is the 3rd time I have the same issue.
Can't point the problem.

The veg time is awesome, quick growth, no burns, amazing leafs:
https://i.invalid.com/irtWNc3.jpg
As soon as 12/12 starts, leafs begin to burn, without any environmental changes:
https://i.invalid.com/51HmMF8.jpg
Than goes downhill fast:
https://i.invalid.com/bnxyn8z.jpg

EC is 1.2, PH 5.8, straight coco.
Temps 27C, RH 70%, good VPD.

Jacks 321 with RO water.

The lighting is a custom DIY panel with 2x Phantom Boards @ 2 amps, 10x Clu048 1212 cobs 97CRI @ 1 amp.
Everything dimmed down to around 30.000 lux.
Sealed room with CO2 only dispensing enough to maintain around 500ppm, not boosting. Exhausting 15min every 2 hours.

I don't know what to do...

 

[diogodasilva]

Veg:

Switch

Flower

 

[DismalDude]

Those leaves look cooked,literally. I would guess lights are too close.

 

[Toaster79]

How much air movement have you got in there? Those leaves are burnt no doubt. Cant put my finger on it but the way those leaves are cupping from the tip towards petiole just don't know. Looks like heat stress to me. Where do you measure your temps? Also when do you switch your veg nutes to flower nutes. Do you make a transition from veg to flower or do you go cold turkey on them? I'd back your lights off some fo starters.

 

[diogodasilva]

How much air movement have you got in there? Those leaves are burnt no doubt. Cant put my finger on it but the way those leaves are cupping from the tip towards petiole just don't know. Looks like heat stress to me. Where do you measure your temps? Also when do you switch your veg nutes to flower nutes. Do you make a transition from veg to flower or do you go cold turkey on them? I'd back your lights off some fo starters.

Hey @Toaster79 thanks for the input.
There is a fan moving air around , just indirect movement, not directly to the plants. It does look heat but the light is LED and dimmed down to 30k lux, around 450ppfd, and 70cm above canopy. My temp sensor is right at canopy height so spot on. And I keep it controlled between 25 to 27C.

AS for the nutes, I run Jacks 321 all the way. Many others have success with this mix but I'm starting to realize that maybe it does not work for me. Could be a Potassium deficiency ?

 

[Toaster79]

They do look like they get hungry where the light intensity is higher. Your humidity is also on the high side, slightly too high. That cupping and shriveling looks like it's got to do with co2. Kinda weird. I'd try feeding more. Bump your feed 150-200 ppm and keep your eyes peeled.

 

[DismalDude]

They do look like they get hungry where the light intensity is higher. Your humidity is also on the high side, slightly too high. That cupping and shriveling looks like it's got to do with co2. Kinda weird. I'd try feeding more. Bump your feed 150-200 ppm and keep your eyes peeled.

I'm sticking to it being a heat issue because those leaves are cooked.Not a deficiency,just cooked.

 

[London bud]

Leaves canoe when they're to hot to long? Personally I think you have a nute problem