Nay
Songster
It is hard to say without complete information. Hopefully some others come along.. but diet, and an incomplete diet could have certainly played a role.Do you think the food killed it?
Seed mixes for outdoor birds have a lot of fat and lower protein than Poultry need. Think about a child raised entirely on candy and treats and whatever they could find in a backyard they would survive but not be very healthy.
You also mention that many other backyard birds come in your yard. They could have picked up a disease from the wild birds.
Or it could have been something else entirely such as egg binding or any number of Poultry afflictions.
I'm very sorry for your loss. But please find a food with proper nutrition for your other one.