I used to be a regular on this forum for a while a few years ago when I moved and got super busy and stopped coming on here.
Anyway Gem is now around 5 years old and is loosing a lot of feathers, it's completely the wrong year for a moult and she hasn't got any pin feathers coming through. She's still eating and drinking normally and going to the toilet normally. It's mostly the mid sized feathers that had been falling out, the most common sized ones. and mostly on her chest and above her tail and under the wings. At first I thought she was just getting scruffy but it's been getting worse and I'm starting to get worried. Her behaviour is still the same and she hasn't been plucking so I don't know what is going on.
Considering the pattern, I would still suspect plucking, even if you don't see her doing it. If nothing has changed in her environment that could explain it, I would get her checked by an avian vet first thing, to help you rule out physical causes.
Quaker Peppy (RIP my sweet pea), CAG Allie, dogs Wanda and Bonnie, feral kitties Cleo and Antoinette, mice Charlotte and Emily, née Jake and Elwood