sorry for your loss....xo's to your dragon now with wings..
temps...28* ...is that at the hot end under basking light & U.V
at cool end or mid range?
i mist my tank when ive changed the tank....to flatten the sand
i bath mine during spring/summer weekly....autumn/winter when they get too grubby,individually (unless brumating)
this & other desert dwellers dont need the thick air caused by misting ...
the other species like Boyds Forest Dragon could take a bit higher humidity...liken to their environment
im really glad you are asking what went wrong.....none of us will probably have a 100% answer
only a reptile vet with knowledge of his full history may have,maybe not?
as we all do,you feel responsible......need answers......
unfortunately.....you may not get all of them...& they wont bring him back
it can happen to anyone....not just you ....
if your thinking of getting another....start fresh....from the beginning
read all you can ...see if you can correct anything you did previously
asking questions is great
smile when you think of him...im sure he is with you!