Get it off the topsoil. Organic or not it’s loaded with bacteria. Heat plus moisture equals more bacteria and that’s the last thing you want. It’s very easy for an opportunistic infection to set in under your circumstances and that’s probably the case. You should take this guy to a vet but if you cannot, get it out of it’s enclosure and into a quarantine tank. A Rubbermaid container with wadded up wet paper towels will do the trick. Change them daily. You can soak it in a honey bath and offer supportive care but again you should see a vet. Generally once symptoms like this present they do not resolve on their own. In the future use coco fiber as a substrate. I hope it improves.