I looked up your previous post - you wrote that these growths come and go, so it's not just a normal discoloration. I would guess some kind of fungal growth/skin disease. I came across this that seems similar but not exactly the same. Your best bet would be to have someone examine some scrapings from the affected areas - your ag extension office, state vet lab, avian vet, etc.
If it is a type of fungus or other skin disease, then hopefully there's something that can cure it. You could try athlete's foot cream or wart remover on one of the spots and see if that helps.
4. MYCOTIC DERMATITIS
Sometimes, there may be epidemic form of dermatitis of the skin of back and thigh regions.
Birds look apparently healthy because the lesions are covered with feathers but on
exposing the skin it is found thickened, yellowish brown and inflamed. The disease is
caused by yeast-like Rhodotorula mucilaginosa. Affected skin shows inflammation, oedema,
congestion and proliferation of fibroblasts.
The fungus can be demonstrated in the skin scrappings or sections by periodic acid
schiff (PAS) staining.