Scale Rot???

[Lord Sorril]

and the temp is 90 F, give or take a bit. Is this something I should be worried about?

I have rarely seen snakes with so much 'scale rot' on the sides unless there is some on the belly as well. It is only a guess from the photo, but, it looks more like fecal matter. Have you tried taking a paper towel and some water and tried gently scrubbing it off?

Also, hopefully 90F is your hot spot temp from an under-tank-heater and not your ambient. 90F is too hot-air temp should be closer to 80F in the entire enclosure.