How often does she get a good soaking-wet kind of bath? That looks like dirt to me. Especially if it's the only place on her body those kind of feathers are present. From the photos, she looks to be in perfect feather everywhere else. Nutritional deficiencies cause ragged feathers all over the body, as well as poor beak and nail health and are typically seen in older birds. You would have to try very hard to make such a young bird start having those issues, and it sounds like you take very good care of your baby. I would find a nutritional deficiency a very very unlikely possibility in a 1 yr old parrot.
My first course of action personally would be a good bath. When parrots eat, or play (some even stick their feet through the bars of their cage), the bottom leg feathers can get quite grungy. Try giving her a bath, and pay extra attention to those feathers with the spray bottle. Sometimes it's bad enough they have to molt out. Kiwi got a hold of spoon with honey on it once and managed to smear it on his wing. The honey feathers got to looking just like that (very dark and kind of matted) once they had picked up dirt from the environment. Didn't matter how many baths he got either, they had to molt out and his new feathers came back in just fine.
And if you are really concerned, take her to a good avian vet for a wellness check. They will examine her and run blood+fecal tests to determine if there is anything she's deficient in, is getting too much of, has a disease whatever.... If anything, it will calm your mind or bring to light something that can be addressed. Sometimes the cost of a vet visit is well worth hearing the bird is healthy just to put you mind at ease.
and I was wondering if that is molting feathers or signs of vitamins deficiency...
