I agree to unplug the RHP until you get the probe. That's a nice one and they can really warm a spot.
Heat kills humidity so if you have a overhead heat source like a bulb, CHE, or RHP they zap the humidity. Thats common.
The simplest fix instead of worrying about the humidity for the entire case is to just put damp moss is both hides. I did this for a long time and still do at times. Works great, is easy, and takes the stress out of getting a good shed.
I have always used the Frog Moss and the XL box gives a good amount.