It has been many years since I worked at Petsmart, but the company has ties with KayTee brand and with all likelihood your dove was fed a Kaytee seed blend at the store, too, and probably its whole life as Diamond Doves from Petsmart come from Kaytee's Preferred Birds facilities. It sounds as if your poor dove was unwell to start with, and stress can make them much more susceptible to illness. I do wish all the best for you and your bird.