Are onions poisonous to dogs?

Are any supplements needed with any Purina One products?

My dog has kidney failure. I have been cooking meats, onion, garlic, potatoes, and then I put them in a food processor. I need a dry food to balance her diet so she doesn't have diarrhea from all the moisture & medicine without sodium added.

Do I need to supplement my pet's diet?

Is it okay to switch between pet food products/flavors?

I have a puppy and an adult dog. Can they eat the same food?