Background: My corn snake is about 2 and a half. He is in a 20 gallon long tank, with an under tank heater at one end. The low temp hovers between 70 and 75, the high between 88 and 95. He has lots of hides and a big water dish. He has about 2 inches of aspen bedding. He used to have a wet hide, but this scale problem showed up so we took it out. His scales improved, and the sheds have broken up since then but otherwise were complete and fine. We feed frozen/thawed and as far as I can find, there is nothing sharp or dangerous in his tank. He's eating and behaving like he always does.
So, now he has this weird scale thing again and I can't think of why or how to address it. It looks almost like he was cut and now it's healing. Any ideas on what's wrong or how I should treat him?