Heat issues? could it be something else??

[aesoprock00]

well, all of my fan leaves on a plant that's been in flower for 4 weeks turned very crispy and are browning in just a few hours.

i've been battling heat issues for a long time now, generally it's 90-100degrees inside my cabinet. i've installed 2 additional exhaust fans, but it hasn't seemed to help at all. could it be the heat that's killing this plant?

in the past, before i installed the 2 newest exhaust fans, all of my plants would steadily turn brown and the fan leaves would get real crispy and die. they are all in separate DWC reservoirs that i fill individually, so i know it's not a general nute or (hopefully not) a pH issue. literally all the fan leaves turn crispy and brown from top to bottom, then it starts in on the leaves in the buds themselves.

i've harvested them all, and the buds are only slightly affected, usually the burnt leaves can be cut away from the buds themselves and it's not much of a problem.

the thing about this plant, and the reason i'm submitting this thread is because for the last 4 weeks while this plant has been in flower, it's stayed green and nice. i thought maybe the fans i put in had finally worked their magic, but i came home from work today and smelled a heavy hay smell, and now i see crispy leaves from top to bottom, and a cabinet temp of 100F.

is it the heat that's causing this problem? the roots look fine and literally yesterday the plant looked just fine too. this will be the 4th plant affected by this crispy fan leave problem and i'm really getting sick of it. any advice, suggestions? Thanks in advance..

i'm going to go looking for a better exhaust system, but is there anyone who doesn't think it's a heat issue? any other thoughts?

 

[pieceofmyheart]

I wonder, I would think too much heat for long periods of time could do that. Isn't there such a thing a bad air syndrome too when plants are locked up too tight without any fresh air reaching them?

 

[aesoprock00]

well, there is certainly a few intake holes at the bottom of the cabinet, plus i open the doors and go back there all the time.

i'm starting to think it might in fact be a nute issue. the heat probably plays a part in it, but as i've had more and more grows under my belt, i've become a little lax about checking PPMs as often as i should.. it's my own fault, i know it. i'm killing them and i just can't stand to see them die!

 

[MTF-Sandman]

Ummm, I have to think that if the temps were in the 90-100 degree range, that yeah...that's your problem.

What's the venting/light/cooling setup of the cab and the ambient room temps?

BTW, if you harvested at 4 weeks then I would say that the buds were dramatically affected by this...

 

[aesoprock00]

Ummm, I have to think that if the temps were in the 90-100 degree range, that yeah...that's your problem.

What's the venting/light/cooling setup of the cab and the ambient room temps?

ambient room temp ranges from about 76-80. 2 passive intake holes at the bottom of the cab. 2 exhaust fans at the top near either light. 2 100w HPS lights, and 2 20w flouro tubes on either side. i'm planning on changing things up with the exhaust situation right now... well, asap.

BTW, if you harvested at 4 weeks then I would say that the buds were dramatically affected by this...

no no, no harvesting at 4 weeks. always at 8. but i'm on a 2 plant cycle where i harvest one every 4 weeks and put a new one into flower. sorry if i was unclear.

 

[MTF-Sandman]

I'd have to say that the exhaust fans aren't pulling enough air...the rest of the setup sounds pretty decent. Muffin/PC fans are notorious for not pulling enough air...especially if there isn't alot of free flowing available to them. Might wanna start by making the passive intakes bigger to ease the back pressure on the fans and if that doesn't help, you'll need to either have an active intake or stronger exhaust fans.

Ahh...that makes more sense now chopping a plant every 4 weeks.

 

[mace_ecam]

Heat stress can be caused by many factors, all of them are related.

Ambient temps
Radiant heat (IR)
RH
Wind
EC in rootzone

If your growbox is hot and dry, adding more wind (fans) will intensivy the problem.

Try to get your temps down and your RH a bit higher (50%), reduce wind, make sure that your bulbs aren't too close to the tops for your (hot) environment.
In environments where the plants have to battle heat and take up more water, reducing the EC could help, makes it easier to take up water and reduces the possibility of nute burn.