Necropsy at a local vet will give some answers. Also did he have an gurgling or weezing sounds? Any sort of dried mucus around the nostrils or constant yawning? Might have had RI. Also, for a BP you want his cool side at 84, and his basking hot side at 90. What sort of mulch was he on? Was it cedar chips by chance? If so that is very toxic to them cause of the oils. Also was is a CB or WC? Sorry to hear about you loss and nothing weird about feeling sad about losing a BP. BP's are pets just like a cat or dog. Except they don't bark at the back door or claw your couch