Hey There,

I'm new to the BP world myself! The only thing that sounded to me that could be contributing to your problem is the heat lamp. Heat lamps tend to dry things out. If you don't have a hide on the cool side he'll have no choice when he's thermo-regulating but to dry himself out under the lamp. I would suggest setting up another source of heat for the cool side and see how that goes..

Hopefully someone will respond soon and give you better ideas.