My puppy is 6 months old. We have had a tricky time getting him to eat dry food. We've tried lots of different makes. He seems to be more interested in Wainwrights from pets at home and also Forthglade which is about twice the price of Wainwrights. Can I mix them and continue this way or should I get him on the one I want him to have? Ideally I need him on the cheaper one but I know that sounds terrible.