Yes,and maybe thats the reason that O.P realize he has no financial help to saving the King,and the parents decide to get him another cham just to make him happy.For the vet to dig deeper, they would need a necroposy or a live animal at least. There is neither now. I also am not disagreeing it could have been kidney or liver failure, which are also both caused by poor supplementation. It could have been something from the wild, however the poor husbandry surely didn't help matters even if it was.
(OP cant afford a Necroposy)