Leaves Folding in Half

Yesss, it's really hot :/ if you can't increase the humidity in the room, you could try using an intake and exhaust fan, positioning it right at the top along with the light panel... that way the cold air passes through. It will help lower the temperature of the light panel and immediately exit through the exhaust in front... obviously, this is achieved with a cooltube and aluminum sleeves, another option is to add an intake fan positioned at the bottom of the cabinet :o

Yes, this is being caused by heat stress. The leaves are curling upwards around the edges to form a canoe-like shape which is an apparent sign of heat stress. Your temperature looks fine so I'm guessing the light is too close, try going 24" inches above the canopy instead of 18" inches, it might be too much for the plant.