If your dogs aren't doing well on a food, then that's not the food for them. I don't feed my dogs any grocery store brand. Years ago we fed Pedigree, but when our dogs started looking poor and not doing as well, we gave it up.
What I look for is a dog food that does not include corn, and that includes a couple major meat/protein sources high in the list of ingredients. I presently feed "Chicken Soup for the Dog Lover's Soul" Adult and "Premium Edge Skin & Coat."
Brands can vary by region, though, so a good place to do some local brand comparison is this website:
http://www.dogfoodadvisor.com/
You can look at brands available at your local feed stores or whatever, and compare them on this site. Purina makes various kinds of dry foods, so you'd have to see what you've got. Their regular Purina Dog Chow gets only 1 star. Purina Pro Plan gets 3. My dog foods both get 4.
There are some top of the line dog foods out there, like "Taste of the Wild," but if you're on a budget, like I am, look around and do some comparisons on that site. That should help!
~ Gloria
You ask of my companions. Hills, sir, and the sundown, and a dog as large as myself that my father bought me. They are better than human beings, because they know but do not tell. ~ Emily Dickinson
To sit with a dog on a hillside on a glorious afternoon is to be back in Eden, where doing nothing was not boring - it was peace. ~ Milan Kundera