I agree a culture needs to be done. I don't think that the animal was loaded up on abos to appear healthy when sold. Sick snakes just don't get better for a day with a bunch of abos. Stress probably compromised his immune system from the beginning of the show. And The new environment just exasurbated it.
I would like to hear about your set up a bit more. Glass or rack?
How are you measuring your temps? It seems like you Have a 10.f variance in your temps from what you said. That's alot of fluctuation.
Roll through your set up again:

Hot side temp
Cold side temp
ambient
Tank or rack
How are you measuring temps
How are you providing humidity


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