Thanks for the posts everyone. I tried the idea of completely drying out the mulch over the weekend and that seemed to work fine. I was worried that my water dish was too big, but in order to make sure which thing was the problem (the substrate or large bowl) I left it in. The humidity is now between 60-65%.

I am now, however, having heating issues. I'm worried that my UTH may be malfunctioning, because it was working perfectly since I got it, for about 5 days, until today. Grrrr.

At least Squiggles will be fine in her tank until I get the tub working well.