Leaf problem???

The temperature difference between your night and day cycles are insanely high!! when growing cannabis you want no more than an 8 degrees Celsius difference (even that is quite extreme) between the cycles, not to mention your crazy high humidity levels during the night cycle. This IS heat damage because when the lights turn on they instantly increase the temperatures by over 10C which causes that stress. Try installing a heater on a timer which turns on when the lights turn off to balance it. If this problem persists (which I doubt will) then it is a root problem! Hope this helps! Good luck and happy growing :)