Do ever spray the snake directly and watch him drink? I actually don't spray my snakes directly all that often except when they're in shed. Spraying them usually induces drinking and I think having them internally hydrated is very important during a shed.
Does he come up and perch/prowl around at night normally? Sometimes they just go through a period of being on the floor. I agree, however, that your temps need to come down. My warm side is around 86 and my cool side is in the mid-high 70's.
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Kimberly Burge
Southern Chondros