Sugar

Caffeine

Alcohol

Junk Food - Chips, French Fries, etc.

Fried or Fatty Foods

Salt

Refined White Flour

Pellets

Vitamin Enriched Products

Chemical Preservatives: ie. Ethoxyquin

Colored Products: Chemical Dyes

Artificial Flavoring

Dairy Products

Corn

Peanuts

Soy Products

Spirulina 

Wheat & All Gluten Grains

Sunflower Seeds

Citrus

Potato: There are lots of chemical residues in potatoes.  They are sprayed.  

Store bought berries.  These are also highly sprayed.  

This is a list of the foods with the most chemical residue:   http://www.birdsnways.com/wisdom/ww18eii.htm 

This is another site that lists possible chemicals in our food and the accepted amounts 

Natural Whole Organic Foods.  Lots of fresh veggies, greens & fruits.

Ground Organic Flaxseed

Alfalfa Powder

Sprouted Seeds (millet, oats, lentils, etc.)

Supplement with a good calcium, magnesium, vitamin A and vitamin D supplement if your bird doesn't get direct sunlight.

As your bird is improving introduce new foods slowly.  It could be a food allergy.  

Give your bird lots of attention.

Give your bird lots of foraging toys and other new toys to keep occupied with.

Give your bird daily exercise.

Give your bird a shower or bath (which ever your bird prefers) at least three times a week.

Work on clicker training or other training techniques.  Teach your bird new things.  

If possible take your bird outside for some fresh air and sunlight.

Get a air cleaner.  We had a dog that used to be itchy and chew himself.  It was amazing how that all stopped when we got a good air cleaner.  

Test for Giardia as it can cause plucking.  Click here for a good article.