Actually the OP's temps. are about the only thing that sounds right...and my 5 corn snakes just voted on that...
Corn snakes are not ball pythons...they thrive with far less heat than BPs, & over-heating them is harmful. They should always have an optional warm corner of their
cage (I prefer to use UTH with a hide over it, along with at least one hide on the unheated side of cage); my ambient room temps. vary by the season from 80* in the
summer to 70* in the winter, and regardless of the season, they are most often on the cool sides of their cages, thermo-regulating & then using the UTH as needed.
They also enjoy a humid hide with damp sphagnum moss inside...on the unheated side as well.
But something seems amiss about the snake's size & age, or the prey being offered.![]()