I'm sorry for your loss. Hearts break even after one day with such incredible creatures.
Only adapt a fully weaned by abundance baby.
Also the stress of a new home can uncover any health issues they were fighting. Young burds are very vulnerable as immune systems aren't fully developed and they have just lost the protection of passed on immunity. They often break with a very common chronic or hidden bacteria infection called parrot fever among other names i have trouble spelling. Its especially tough on young birds, older birds can beat it or develop a hidden infection that can break years later if they are stressed or fighting a new different health issues. I consider that all parrots have been exposed to this clymidia bacteria at some point. Certainly this doesn't have to be your issue at all. But it's why I do the following
Any new burd that I bring home, even old ones. I provide supplemental warmth fir a few days. I use a radiant heat panel called the sweeter heater. Never use a heat lamp. Extra warmth is so helpful. I also make sure they have millet, treat Stix, and what ever food they were in. Often birds go off or light on food the first few days in a new home. So I try and offer lots of yummiest stuff.
There are many household toxins that can kill burds. Off Gass from instapot, nonstick cookware, air fries ect can kill them, anywhere in the home even on a different floor and behind closed doors. Some ironing boards now have nonstick applied that us also deadly. Be sure and research all the articles on household dangers for burds.
Truly I'm saddened and sorry for your loss. It seems like many vets will say "heart issues" when there is a sudden death, to make things easier,.....I'm a believer in truth, so I find "heart issues " a disappointment from vets