Don't know if your budget can handle it, but The Honest Kitchen Dehydrated Food is 100% human grade food. Many people have had great success with this food. They have one called - Zeal -NON Grain - for sensitive stomachs.
Zeal (Fish, Grain Free)
10# = $106 Makes 40 pounds but you actually feed more than you would kibble.
"One of our most popular dog foods, Zeal is higher in protein and low in fat and carbohydrates. Because Zeal is a limited ingredient diet, it’s especially suited for pups who do better without certain pet food ingredients, like poultry, flax and white potatoes." Zeal - Grain Free Dog Food For Sensitive Dogs | The Honest Kitchen
You should also be adding a digestive enzyme/probiotic for gut health.
Here are two excellent human grade products.
Sunday Sundae Nutritional Supplement
The Wholistic Pet
Watch the treats you are feeding.
Grain free treats:
Bravo Bonus Bites: are 100% all meat, and made from all natural, antibiotic-free, grain free meats and organ meat protein sources.
Example: "Dry Roasted" Buffalo Liver: Ingredients Grass-fed buffalo liver.
"Freeze Dried Treats" - Venison Liver: Ingredients Grass-fed venison liver.
Example: "Turkey Bites" - Ingredients: Turkey thigh meat.
Pet Supplies Plus : Home Page
The Honest Kitchen Treats Locate a store: Where to Buy Honest Kitchen - Honest Kitchen Stores | The Honest Kitchen
Beams: a natural dehydrated fish dog treat! They’re made from pure, wild-caught Atlantic Catfish* skins, from the clean ocean waters of Iceland, dried into savory, chewy sticks. They’re guaranteed to satisfy the pickiest of pups and are the perfect treat alternative to dried chicken snacks or bully sticks. Beams, like all our products, contain no Chinese ingredients!
Nuzzles: made with duck & cherries.
Fromm's four star grain free is also a good product. http://frommfamily.com/products/four-star/dog
Always introduce a new food or supplement slowly.