Problem with top leaves
- Thread starter speed420
- Start date
hotrodharley
Well-Known Member
If there’s not a fan blowing on it I’ll say nitrogen overdose.
Wouldnt it canoe up not down due to shading and how they take in the light? Ive seen this many times with lighting but never in a downward position
macsnax
Well-Known Member
Ya it took me a minute to figure it out when it happened. Think of it as stress rather than burning due to a switch up in intensity. My wifi popped 3 stress balls because of it too. I'm not 100% that's what he has going here, but it looks similar.
speed420
Active Member
I got 2 fan blowing on them but on low. They are on 480watts cmh light in a 4x4 tent. My temps hit 80 sometimes then got to run ac to bring them back down my RH is 50%. That plant is a Cheese XXL my other 3 plants have no issues. I am watering every second day with AN grow/micro/bloom in coco/pl mix with a ppm around 300. I have never seen this happen with any of my plants before.
DocofRock
Well-Known Member
It looks like a transpiration problem inducing some micronutrient deficiency IMO. How close are your lights? Maybe you’re getting humidity spikes during lights off + overwatering causing your soil to stay too moist? Maybe your lights are too close? There’s a lot of possibilities. Do you evaluate your VPD? Do you use RO water? There’s a lot of potential issues that you might not give any mind, at least in my experience.
I was just wondering cause i seen pics like that but idk why. Mine always go up due to heat and lighting issues
macsnax
Well-Known Member
I think the difference is intensity VS heat. It was new to me when I switched to cobs. They don't put off UV like HID lighting, so intensity can be pretty high with acceptable leaf temps.
DocofRock
Well-Known Member
And, I’d say if your leaf surface temps are >82, that’s a big problem because of this very thing. I struggled to get my LST above 77 for the longest time, even with lights that were too close/intense. You actually often have to try to increase LST when using LEDs due to the absence of IR. Ambient temps often have to be higher with LED than other (HID mostly) lights to heat the leaves enough to reach the optimal metabolic rate of the plant. That said, LED are powerful enough (I’m talking QBs/COBs) to burn your plants, even when your temps and LST are within acceptable limits.
macsnax
Well-Known Member
Ya I guess I could have clarified that. I'm not saying that led's won't burn plants. I didn't take it that far, I just had the pot turned up a lil high for distance to canopy. I use an ir temp gun in my grow, I know the temp of everthing, lol. It's actually pretty handy, especially trying to dial in vpd.
rkymtnman
Well-Known Member
what leaf temp are you shooting for? and what is your watt/sq foot with the cobs?
macsnax
Well-Known Member
I'm running 39.375 watts per square foot. When that happened to me I was running 79f leaf temps. But those plants had just came from under a cheapo led. I use those for seed starting and cloning. It's not 50 a square, but I did just pull 280ish g off one plant under those.
macsnax
Well-Known Member
Autos seem to be sensitive in general. The two plants that I had show that were 2 out of 5 in that tent. I don't think I've asked you much for details. What is the light? How far from canopy?
speed420
Active Member
I am using a 680 watt CMH light have it set to 480 watts right now but turned it back to 350 watts. the light is almost 3 feet away. I am running the ac now so the temps dropped down to 72F
macsnax
Well-Known Member
If you narrow it down to not being from your lights. I would to root issues. Maybe a shot of hydrogaurd or southern ag just for good measure..... Or did this happen, and then you dialed the light down?
speed420
Active Member
I dialed the light down after this problem. hoping the lower wattage and the ac running to keep cooler temps will fix this problem.