I am a newbie also, and I was having the same problems you are. I had one UTH which was keeping the warm side at 90, but my cool side was very cold, so I threw a heat lamp up there. I quickly realized the heat lamp was SUCKING the humidity up.

Solution: I ditched the mesh top (I had one like you) and I went out and got a 20x10 piece of plexiglass. I cut the mesh out of the metal frame and glued the plexiglass back into the metal frame. Then, I went out and got a small UTH for the cool side, hooked up to a rheostat.

As of now, my temps are great and humidity is just dandy.
PLEASE get rid of the mesh top, they're horrible! You will keep having problems with it.

Oh and that 20x10 piece of plexiglass was only $5.00!