Great suggestion! Thanks I'm gonna look up that salt test and give it a shot! And I never thought about drying out the substrate first. I'm gonna do that next time I change them. I've been changing their bins way too often - just because I was trying to sort out the humidity issues. I was just worried about scale rot and RI's LOL. They've been through a lot with their previous owners and I don't want to add illness to it.
Cheers!