I'd take him/her to the vet, like everyone else said it could be in need of some sort of surgery, as it could be anything, definitely quarantine though, as it could even be some sort of parasitic problem, and if it turns out to be parasites, you may want to go ahead, and have your other snakes checked out, parasites spread easily. I don't know how much it costs where you live, but it's $50 for physical/exam on exotics where I live, and it's worth it.