An extreme nose-up or nose-down position is usually an early sign of dropsy--something that occurs as a consequence of organ failure. This is too bad, it seemed like he was really doing well, too. But it's possible he had organ damage earlier on and that may have been the root of his problems to begin with.
I hope I am wrong, but if he starts pineconing, you can try to dose him with some epsom salt and see if he makes any improvement. If you don't have any epsom salt around, I hate to jinx it, but it might be prudent to go purchase some. :(