Hmm.. I don't know for parrots, but I know for people: carrots and celery (silica), walnuts and flax seed (omega 3s), spinach, kale, sweet potatoes (vitamin A), berries (anti-oxidants and vitamin C).
Also, do you give him baths/showers? That would probably help with dry skin if it isn't something he gets frequently already. I see you live in North Carolina, which isn't a dry place, but A/C and heaters can dry out the air. I run a humidifier in my bird room (you can pick'em up cheap).
I carry his cage outside every day when it's nice. He has a large pirex dish with water. He likes to lay in it and bathe every 2-3 days. We live in the mountains so it's not as hot as the big cities. It is VERY humid. It's been around 100% for days now. We don't often run the A/C. Crusso's a bit strange in that he won't eat nuts or berries. He likes banana and strawberries tho'. Otherwise he mainly likes to eat his pellets.
My avian vet advised me that most captive parrots are deficient in vitamin A. This vitamin is beneficial to their skin and plumage health. Try to feed him produce rich in vitamin A (google list). Also add more humidity to your home. Most of the time air in homes are very dry. It's good to keep it above 50%. Add a humidifier or two, and some house plants both potted and in water vases.