hello,
I've recently purchased a male Eclectus. And the breeder sent me a photo of something she's never seen before, he is only around 10 weeks old and has recently started to GROW black feathers. The other babies are all on the same food. And nothing is wrong with the others.
I have seen this in birds from time to time, especially in younger birds. This represents a weak feather pigmentation. This will sometimes go away after first molt provided the bird has a proper diet. Too much of a seed and pellet diet will do this to younger birds. Don't hesitate to change up the diet to protein snacks, oil based snacks ( give my birds flax seed oil in their morning steel cut oat cereal for breakfast). They have beautiful feathers and coat. A little fat in the diet once in a while will not harm your bird. My birds have tried everything in way of food. Hot chocolate, sharp cheddar cheese, green tea, pizza, ect....they are extremely healthy and lively birds.
The vet even commented saying " this was one of the healthiest trio of birds he's seen in a while, what sort of diet do you feed them?" Ha ha ha,,,I said everything, they aren't choosy. Of course they don't get it everyday nor get large amounts...Especially like my wife's meat loaf which they dive in literally....and smelt ...they love fish. And of course they like jalapenos and chilies.
My point is, feather pigmentation is in the birds make up or metabolism, some birds are slower than others at first. My Senegal is the smallest Senegal the vet ever seen at nearly 3 years old, he's not much bigger than a parrolet. That's small, or very petite for a Senegal. But he's healthy as an Ox.
The Black feathers I'm not concerned with in a younger bird, it is something to keep an eye on as if it was say, an older bird that developed black feathers I'd be very concerned as it is a sign of cancer, and or internal disease. In chickens it is a deadly sign.