It appears that diet and even vitamin deficiencies might be at the root cause. To eliminate any medical cause, a trip to a certified avian vet might be in order. A number of sites mention that lighting can be the problem and recommend special lighting. Here are a few sources that I found to let you determine for yourself if you need to adjust anything in your bird's life.
- "Feather Discoloration," 8/15/09, BirdTricks.com - http://www.birdtricks.com/blog/feather-discoloration-and-dull-plumage/
- "Feather Disorders in our Pet Parrot's," 11/18/09, articlesbase.com - http://www.articlesbase.com/pets-articles/feather-disorders-in-our-pet-parrots-726620.html
- Thrush, Patrick R. "Lighting and Your Bird," (reprinted from the NCS Journal July/August 1999, Vol. XVI, No. 4) - http://www.mmlights.com/bird%20lights.html
- "Birds Need Light - Natural or Full Spectrum UV Lighting: Essential Lighting For A Healthy Bird - http://www.drsfostersmith.com/pic/article.cfm?aid=1015
- "Feather Quality and Skin Condition are Nutrition-Related" - http://www.drsfostersmith.com/pic/article.cfm?dept_id=&aid=1012
- "Full Spectrum Light for Birds that you can use in regular light fixtures and the AvianSun lamps" - http://www.parrot-and-conure-world.com/full-spectrum-light-for-birds.html
- Beaudoin, Terry. "The Necessity of Full-Spectrum Lighting" - http://www.parrotislandinc.com/articles/alight.htm
