I keep my dogs and cats on Taste of the Wild. They are a very reasonably priced grain-free pet food. You can get it at any Theisans or farm store. My dog and cat thrive on it. It is very possible that your pet has an allergy to something in the Purina food. I would try switching food first. Using an elevated bowl can have positive and negative effects on pet's stomachs.
Good luck!!
Good luck!!