My Lorikeet, has large patches of missing feathers with down feathers in their place,and has been like this since I found him. He is fed on Wombaroo nectar mix and fruit and for a while I was giving him a vitamin supplement. I thought with good diet the problem would go but has remained after about 2 years. There is no sign of pests on him and he does not appear to pluck himself or lose undue amounts of feathers, they just don't grow. I would really appreciate some advice on possible causes of this.

Where are you from? Canberra