Not going to act like an expert or anything, but these are my two cents. First off, I hope you didn't buy three different bags of food trying to please them.

Secondly, I would find some way to make the good food (wellness, etc) more appetizing to the pup. Rather than resorting to puppy chow. I WOULD THINK, once the pup realizes that they aren't getting puppy chow that they will eat what is in front of them. I know puppies are suppose to eat more and more often, but to a certain extent I wouldn't give them any other choice. Add some canned food to the dry stuff and put it there, if they don't eat it, then no treats or anything. They'll get hungry, and they'll eat it eventually.