I have always fed my 10 year old lab and 4 year old chaweier Purina dog chow. I recently discovered how horrible this dog food is for them, so I began the switch to Blue Buffalo chicken and rice adult formula dog food. Today, 4 days after we began the switch they are eating 50% Purina and 50% Blue Buffalo. I was sitting on the couch next to my Chaweiner when she vomited up a big brown glob of dog food. This is the first time she has puked in the house, and usually there is usually a lot of grass in their vomit. My lab has been itching a LOT lately, and I don't think it is from fleas because we give them Advantage flea medicine every month. I looked around the yard for more vomit, diarhea, or bloody stools, but didn't find any. I grabbed a handful of Blue and a handful of Purina, and they both ate out of the hand with Blue Buffalo in it. They prefer to eat Blue Buffalo, but I think it is making them sick. Should I switch them back to Purina or a different food and return the Blue Buffalo? And is there maybe a good dog food that doesn't cost so much? Thank you, I am really worried about them.