Small snakes usually do not go off food that is an adult trick.
Temps and security are usually the big issues with small snakes not feeding.
90 for a hot spot is fine assuming it is measured INSIDE the hot hide.
The cool end should be around 80ºF and not lower than 77º again measured inside the hot hide. The ambient air temp should run around 77-85 kinda range it often varies a bit as the room varies. It can be measured from 1/3 up the side and between the hot and cool ends.