How are you measuring humidity? I'm in WA and I use rack systems and my room humidity is 30-40% solid. I have 7 holes on the front and back SIDES of the tub and that keeps me perfectly at 60%. I move the waterbowl over my heat tape when they are about to shed but that gives me about 70-75%. Something doesn't seem right because with that many holes I have trouble believing your humidity numbers are correct.

Dimmers are always going to go up and down the ambient room temp. That's why dimmers only work well in temp controlled rooms. Thermostats can take into account that variance and keep a solid temp. Your cool side isn't going to go up with your room temp at that level. A UTH or tape will only raise the temps a few degrees over ambient unless they are in a tight enclosed rack.

Regards,

B