Heat stress @ 80 degrees?

Could some plants develop signs of heat stress at 80 degrees? I am having a problem with my 400 watt MH and leaves starting to curl. As soon as I spotted it I moved the light up about 2 feet and the leaves actually came back and didn't die on me.

New leaves starting growing normally again and the plants grew about 6 inches more in height. Then the same problem started again. Temps at the top of the plants were 80.5 degrees max and 78.5 min. I have some Lemon OG in there along with the OG #18. The Lemon seems to be a little stronger but the #18 has major problems with leaf curl. The MH is at least 40" away from the tops and I can put my hand under the glass without much heat at all.

I'm starting to get frustrated because I can't quite put my finger on the leaf curling issue. All plants are in Fox Farm soil and no feeding has been done at all. They exhibit all signs of heat stress but the temps are in tolerable range. I have no way to lower the temps.

Could something be wrong with the light itself that is causing the leaves to curl? Clueless....

man you got me..... it almost has to be the light. 80 will never hurt anything unless it was bred to be in 50f wheather all the time. (no such)

overwater is your next guess and i almost bet thats what it is....... got any pics ?

what kind of ff soil. ocean forest or happy frog?

Ocean Forest. I only water when they are almost totally dry. The leaves look different when they are affected by water.

I moved the light up and the next 2 new sets of leaves were fine. Then it started happening again once they grew taller. I never heard of the light causing leaves to curl up and start dying at the edges. I have nothing to take pics with.

Are they growing taller, or are they stretching?

Both. They definitely stretched after I moved the light up but they also grew 2 new sets since that move. The topmost set is starting to curl on the OG #18's after that 6" growth spurt.

The light in question is a Hortilux 400 watt MH. It's a bit over a year old now and it's constantly running.

What I want to know is if a light can cause the heat stress effect on the leaves without it being hot. Because my temps are really damn good.

ocean forest is sometimes too hot for babies. it will grow right into it. nothing to worry about as long as its growing and green. the curls are from a tiny bit too much food if you are SURE your not leaving the soil too moist.

no big deal






soil