I don't think that's it, leaves are still soft, plus my females are closer. I have the lights set to the same height for par output (the one above the male is 8" higher). I have turned the cobs off on the one above the male, about a week ago, thinking the same thing, but it has not slowed the curling. My temp sits at approx 75 to 80 during the day and 68 to 70 when lights are off. Rh is approx 45 to 55. This is a cherry wine hemp male btw. (The one behind him is a cherry wine male and the two to the right are black d.o.g. og. From Humboldt seeds)