Sun conure baby died

by frank diaz
(miami, florida)

I have a pair of Sun Conure with 3 babies, 2 weeks old, checking the nest box yesterday afternoon I noticed that one of the baby was apart from the rest, very weak, cold and with the crop empty, I took it immediately, I hand fed him and heat him in a 10 gallon tank with a heating pad @ 88 degree.

After three hours I noticed that the crop looked like a balloon full of gas with no food on it, I could remove the gas massaging the crop, then I fed him for the second time. Before going to the bed I checked it and everything seemed to be ok, he was firmly stand in his legs and trying to open his eyes, but this morning when I wake up at 5:00 am, he was died with the crop full of gas and drop of handfeeding formula in his nose and mouth. Do you have any answer to this? How to avoid this in a future?