I'd drop those temps. Schrenckii like the ambient in the mid to low 70s with a cool end down in the low 70s.
This is about the time of year that my schrenckii go off feed and I brumate them. These are animals that brumate for a little less than half the year in the wild. If he's refusing food, don't feed him for a another couple of weeks and then gradually drop the temps. I brumate mine at about 50 degrees for 12 to 16 weeks.
Just out of curiosity what size prey are you feeding him? My largest adults don't get anything as large as a rat...............if you don't want to brumate him, try feeding him several smaller prey items - like small mice - and see if that doesn't pique his interest.