Okay, nothing in that setup that should cause something like that. Still put him in the hospital setup like I described though; you don't want bedding getting into that place, and cocofiber is the worst for that because the particles are so tiny. Especially since you said there's residue; it'll stick to anything that's even a little bit wet.

I still say vet though. I think this is at the point he's going to need antibiotics, and they can also probably tell you if this is related to the breeder sexing him in any way, which should be grounds for either another snake or a refund for the vet bills if they aren't a totally terrible person (honestly if a vet confirmed this was related to sexing him improperly, I'd tell him he could either refund my vet bill or have his name and business outed to the entire reptile community as a disreputable place you should never buy from... that'd probably get his attention). I've never seen something like this from sexing, but when you buy from a random Craigslist person you never know if they're legit or if they have no idea what they're doing, so I guess that's not outside the realm of possibility. That place could also just as easily not be related to sexing though; vet's the only way to get any conclusive evidence of it.