Heat can cause misshapen high leaves like that but they typically cup UPWARDS.
That looks to me like your plant is root bound.
How tall is it and what is the volume of dirt? You want approximately 4 L soil per foot of plant.
Other things that can cause that are overwatering and not enough ventilation.

Are you growing in kitty litter pans?
I personally think that a container that is DEEPER for its volume is a more efficient use of floor space as you can cluster plants closer together btw.
stinkyattic Reviewed by stinkyattic on . curling leaves on budding plant,please help have them in pro-mix,plant is about 18 inches high,budding for 4 weeks under 2 warm and 2 cool 23 and 42 watt compact flouro`s and a 70 watt hps. temp is about 83 degrees,still feeding at 1\4 strenght ferts, the leaves are green and the color looks good,they are just curling at the top Rating: 5