How just under 90 is the temps? Are you measuring from inside the hot hide?

Something many fail to figure is small snakes have a faster metabolism than larger snakes do and digestion generates heat so a little snake will actually raise the temp inside the hide a degree or two anyway. Some use 88 as a hot spot for small balls.

Personally given the poor accuracy that prevalent in the hobby I don't like seeing temps over 91º and prefer 90º as it is safer. (digital accuracy common on inexpensive instruments is +/-2ºF it is often better than 2º but are rarely perfectly correct, usually it is about a degree off up or down but more is not uncommon.)