Yeah, he's just shedding. If he has a huge amount of dried substrate or it seems to be sticking, you can soak him or something. Mine is pretty chill, so if she has a bunch of dried substrate on her when she comes out of her burrow to shed I will very gently pour a little of her misting water over her back to get the larger chunks of it off (she's pretty calm and it doesn't seem to bother her at all).