Your plants are transpiring to much that's why they taco. Some strains are more sensitive to intense light. 24 inch away for the light is typically good but nothing is cut and dry. Move the light up and see if it helps. It could also be no correlation and could just be that the plant is done for the day and is not transpiring the way it does during day because it knows it's gonna be lights out soon.
I've had plants where I can hang my LED inches away and other plants where I needed it a couple feet away. If this only occurs when the lights go out it doesn't seem like it could be much of anything else. Maybe mist your plants a bit in conjunction with the humidifier. Might also be hands to have a thermal laser gun to see if you have any hot spots in the tent.