Aspen never did anything for me humidity wise.

Id change the substrate out in one tub to see if it helps, that way your not wasting a bunch on all the tubs if it doesnt work.

Get the ambient temps down, warmer tub, warmer water, more evaporation, more humidity.

Get a fan going in the room to circulate air. Ceiling fans are great.

Ditch the top to the bowl, I've heard horror stories of snakes drowning in bowls with little access holes like that.