My puppy isn't eating very much...?

My Shiba puppy is 10 weeks old, and he's not eating very much. The breeder was giving him Royal Canin, but we bought Natural Choice and tried changing him over to the new food. No luck, so we went and bought a big bag of Royal Canin. We measure out a cup for him and see how much he eats during the day... About 1/2 a cup. He's playful and the vet says he's healthy, he doesn't show any signs of being sick at all. I personally think one problem is my BF was boiling chicken breasts and giving it to him as reward treats ( since he doesn't really like the liver training treats we got him ). I personally think all he wants is to eat chicken... He gobbles it right down if we give him a piece. Is he playing some puppy mind tricks on us to get us to give him chicken...? And how can I get him to eat his food again?