Oh hey, these are such beautiful creatures, & it hurts to lose one! Especially "out of the blue" like this was- I'd have been shocked also. Snakes are very stoic about symptoms, & nothing you mentioned was a red flag- not even the lack of appetite from such a new snake. I know all too well how little sympathy most people have about things like this. (I have no experience with BRBs either, btw.)