I think everything is fine. They know where they need to go to get the right temps. Sounds like you've got it dialed in perfectly. It's normal for them to go on the cool side for a while. Also since they're so largely nocturnal, she could well be going back and forth while you're sleeping. My lesser is a weirdo like that... Consensus is that balls don't bask, right? But he'll go and lay on his branch under the lamp for a whole day at a time, even though his air and ground temps are perfect.

So don't sweat it... As long as there's no indications of distress, everything is alright.