Ambient temps in the cage of 70-72* sounds fine, but I'm wondering HOW MUCH-? of her cage is affected by the 90* heat mat (it's too hot!) and also how you
are measuring the ambient temps. I'd take the jars out & use a normal water bowl, as cute as the jar thing was...soaking constantly, she can end up with skin
issues. BE SURE there are no mites (LOOK AGAIN). Black rat snakes are native to many eastern U.S. states (including mine) which are more humid, but I used to
keep & breed "albino" (amelanistic) black rat snakes back when I lived in the desert with low humidity too. Make sure she has a bowl that is big enough to soak
if she wants, but I really think you need to work on the suitability of her hides, as these snakes don't usually burrow. Make sure she has both a warm & unheated
hide, & bear in mind that these snakes would absolutely brumate in the wild, so that's what she may be trying to do (when cooling off in the jar). The length of
daylight & cooler ambient temps are probably confusing her, since she's still eating. No trouble digesting, I assume? Stools look normal? What kind of enclosure
is this? Not a glass tank, I'm assuming? These do best with air circulation...heat builds up fast in a plastic cage...I recommend & only use glass tanks with screen
tops, FYI.