When we had a screen lid we used to eco earth expandable bedding - it retains humidity better than any other substrate. Also moss can help too but you have to soak it every few days.
I'll look into that! I've been meaning to get moss for his hides when he's in shed, but a bedding change might be in order too. Waiting on the digitial hygrometer right now to get some solid readings and I'll decide how to proceed from there, of course. Thank you!