before the pellets he's been eating mostly millet.
I don't have other birds, but sunny came from a pet store that had horrific overcrowding, i wouldn't buy from them but he was a gift from family. since he came here he hasnt had contact with other birds though.
when I first got him his feathering, including the face, was pretty much normal overall but his face feathers have been getting sparser along with his flight and tail feathers.
as for mites, I do recall seeing a few small mite-adjacent dots on sunnys head when I first got him but that was in 2021 and I haven't seen anything similar since. I remember not thinking much of it since I didn't really know a whole lot about birds in 2021