To be honest I'm having a bit of a problem getting the temps to stabilize where they need to be. I've got a 75watt red heat lamp and a medium sized zoomed uth working together on the basking side and its hanging right around 79.3 - 81.2 (measured with digital thermometer w/ probe). It's the same exact setup as I use with my snakes and I never have any issues with getting the temps right. I've got it in a walk-in closet so drafts aren't an issue. This afternoon I'll get a 100watt bulb and see what happens.
Aside from changing water I'll try not bothering her for a week or so and see what happens.