You've only had this snake a month, so it would be FAR less stressful for him if you do NOT bathe him, but just wipe him off with a damp paper towel.
Is it possible you are over-feeding him? or perhaps he's going into a shed cycle soon (snakes seem to know before we can see any evidence) & that's why he didn't eat.
It's possible if you aren't thawing the rats properly that the latest one (he didn't eat) may have been too spoiled & that's why he refused. This is a common problem.
Thaw in cold water until soft thru-out (feel by hand to make sure), then briefly warm in very warm water & briefly use a blow-dryer if needed. Food thaws faster in water
than in air...by a LOT. Air is actually an insulator- it impairs the loss of heat or cold. And don't use HOT water...it allows spoilage: remember that rodents are FULL of
bacteria (they're whole animals with GI tract full of bacteria!), just waiting for the temps. to be warm enough to proliferate (grow like crazy!). Snakes have an excellent
sense of smell, & BPs are NOT consumers of carrion...they want fresh prey, not rotten.
Don't offer food again for at least 2 weeks, & then, ONLY IF he's not in shed.