Two birds dead with no necropsy results as to why

[JustMyFids]

* posting for a friend *
A friend of mine adopted two Green cheek conures in mid/late 2023, a 3 yr old and a 5 yr old. They lived in a birdroom with 14 other birds and were all caged separately. At the start of this year, they were both found dead at the same time with no prior symptoms of any kind. The 3 yr old GCC was brought in for a necropsy, and there wasn’t any conclusive cause of death. Just wanted to hop on here and see if you guys can find anything that the vet missed or didn’t tell us?
No toxins like candles or teflon are ever used in the house, their diet consisted of Zupreem/Harrisons pellets, chop, and seeds for training. Diet and living conditions are unknown prior to adoption. Both birds were fully disease tested and had bloodwork done which came back perfect mid 2023. Thanks!

 

[Pixiebeak]

The bird is reported to be very thin. At 2 you can have sudden death , especially if was a rapid weight loss ...like switching the diet to quickly...... unfortunately this happens all to often when people get birds on a seed diet and want them eating pellets and rush ( semi -force) a diet conversion...while the birds may start eating the pellets they aren't eating enough to maintain weight, and are actually starving. It's especially awful because it's done with the best of intentions.
That would be my first guess