Thanks so much, everyone, for your responses. I wanted to reply last night but the site was down for me.
I didn't soak him last night after hearing unanimously that it shouldn't be scale rot. I guess the benefit of all of this is that I now know where to find Betadine in my area! I also really appreciate the added help and information provided in answering my other questions.
I got him onto some newspaper yesterday before I realized these responses came in, but I will be switching back to his regular substrate and checking my decor to prevent future problems. He should be due for a shed soon, though I hadn't documented his last shed so I'm just waiting to see signs. It makes sense that it might just be some dirt; I guess the "WebMD effect" just got the best of me.
Thanks again!