The marijuana plant is losing water via it’s leaves faster than what can be replaced by the root system. The marijuana leaf responds by leaf margin cupping or rolling up or down (most times up) in order to conserve moisture. A good example is reflected by the appearance of broad-bladed turf grass on a hot summer day, high noon, with low soil moisture levels - the leaf blade will roll upward/inward with the grass taking on a dull, greyish-green appearance. Upon sunrise when moisture levels have returned to normal, the leaf blade will be flat. Lower the heat in the marijuana grow-op and concentrate on developing a large robust root system. An efficient and effective root system will go a long way to prevent heat induced pot leaf dessication or marijuana leaf margin curling.
Probably just getting a little warm.. If light is close move away and just make sure they get some sort of air moving fresh air.. When you open that door you want them leaves moving.. Think of you on a hot day baking in sun with no shade or fan.. :) Plants look great otherwise.. you don't have a ph issue plants look in good health.. No worries besides just a little heat symptoms :)
