Bunny Buddy
Wise Old Thumper
Try not to be too vexed if you don't find the cause, hard as it is. If you can have a lot of major bad things ruled out and find a way of managing it then it is not the end of the world. We never found out what was wrong with Shadow until we lost him under GA. He had several episodes of losing weight and not been in great health but it was incredibly hard to find out exactly what was wrong with him before the PM as he had a congenital problem with his liver, one that FHB had never come across in a rabbit before You might just have to accept that he needs TLC. I do hope you get some clear answers though, I know it's much easier to deal with both practically and emotionally.