My dad mixed Blue Buffalo with Purina Puppy Chow!!?

So we have an American Pitbull Terrier 5 month old right now and when we first got him he was about 2 month and his previous owner fed him Purina Puppy Chow. Well I noticed that he had allergies so I changed it to Blue Buffalo for Puppies and I have been feeding him ever since and he barely had any allergies but today my dad being very cheap took the left over Purina Puppy Chow which was kind of a lot and mixed it all in with the Blue Buffalo. I didn't notice it until he told me and well my puppy again is scratching himself a lot so now I am pissed off. The fact is I AM THE ONE WHO BUYS THE DOG FOOD NOT HIM. I SPEND $40 ON IT AND NOW IM JUST WTF. There was like half of Blue Buffalo and now the bag is almost full mixed with Puppy Chow. So I was wondering should I keep feeding my puppy the mixed dog food or should I buy a brand new one? I don't care if I have to buy a new one but my dad would get pissed for spending MY money on it and I am not going to just sit in my garage picking out individual pieces of Puppy Chow.. Thanks in advance and sorry I am very pissed right now..