Leaf Curl - Doesn't seem to be the usual suspects

[Theta]

I have 5 plants/strains

2 of them on the far side of a 4x4 light are are curling while the others are doing fine.

I checked for mites with a 100x scope and they are very clean looking also the issue isn't spreading except for the young leaves of the 2 plants







Plants are in late veg in 3 gallon coco

Fertilizer: Athena Pro w/ silica @ 750ppm - Runoff at 900ppms 5.9Ph

Temps 77-80

Rh: 59%

IPM: Lost Coast plant therapy

Lights 680w LED dimmed to 270w they are about 3 feet away as well.

Fan: 16' oscillating fan no longer hitting the canopy directly

The plants definitely are more curled at night and there are no signs of deficiency on older leaves.




I topped the plants before this started happening.




Currently I have the following ideas but I could be wrong.




1.) Not enough calcium?

2.) Root rot issue?

3.) Topping stress but it seems to continue with new leaves.

 

[CrustyCruz]

Maybe multiple issues (1st pic) but calcium availability is one.

I've been loosely following the cannabis grow scene since the 80s and there's not a single cannabis specific source thats up on leaf morphology deficiencies. I'm fairly certain none of the guys at high times, Robert Clarke, Dave Watson, any of the expert book writers have actually touched a watering can in their entire lives. It's weird. It's created an entire lost generation of pseudo gnosis.

I'm gonna keep bringing attention to the fact that the most expensive, "most researched" crop on earth, the one that's apparently gonna change the Ag world, has this moat of ignorance and disinformation around it.

 

[Theta]

Maybe multiple issues (1st pic) but calcium availability is one.

I've been loosely following the cannabis grow scene since the 80s and there's not a single cannabis specific source thats up on leaf morphology deficiencies. I'm fairly certain none of the guys at high times, Robert Clarke, Dave Watson, any of the expert book writers have actually touched a watering can in their entire lives. It's weird. It's created an entire lost generation of pseudo gnosis.

I'm gonna keep bringing attention to the fact that the most expensive, "most researched" crop on earth, the one that's apparently gonna change the Ag world, has this moat of ignorance and disinformation around it.

Thank you!

I think you are correct, because I have been checking for mites everyday and no luck. I was one part relieved but also confused.

Then I dimmed the lights, reduced the temp and increased the humidity but the plants were thriving at 82F/56% so it doesn't react to VPD.

The other change I made was switching from hand watering to netafim drippers and using 55 gallon res. With the hand watering I was stacking with some runoff but with netafim I was flushing a bit more. The runoff ppms went from 12-1300 to around 920.

 

[BobChronic6505]

Leafhoppers can make leaves do weird stuff like that...that's what I've been fighting all summer

 

[Creeperpark]

Heat and low moisture can cause the edges of the leaves to die back, then twist and curl. Its a self- defense response, where leaves and leaflets curl slightly to prevent further water loss. When you topped the plants there was a loss of moisture from the plant making a scab in low humidify. Your plants should come back with the right nutrient hydration. I would turn my lights back higher, full steam ahead and just hydrate more.