Parrot let missing feathers

by mary
(Indiana)

I have a pacific green parrot let I brought from a breeder through a pet store 4 years ago, she still doesn't have feathers on her chest just down but she has the rest of her feathers. I am home with her all day and have never seen her plucking her down or feathers. She will loose some down and then it grows right back and the spot is maybe 2cm large.
Is it possible the breeder may have let her go too soon. There was 3 times he delayed me getting her. The pet shop I got her from wasn't the best it has been closed for a couple of years now.
Is there any thing you could suggest I give her in her food. I have a full spectrum light up above her cage. Her cage is 34H not counting the stand X 21W and she has tons of toys and I rotate them out so she doesn't get bored with them. Other than the feathers she is perfectly happy and in charge of the whole house.
If you have any idea and could tell me what I can do for her or if this isn't going to hurt her I would appreciate it. The picture is not very good she is camera shy.