[My baby Milo]

My Milo stoped eating his natural balance grain free duck and potato. He was on it for about a year. I bought a new bag and he won't touch it all of a sudden. so i go to pet store and got him earthborn grain free bison. That was all they had that was a grain free without chicken. They did have some more of the natural balance different flavor but i wanted a different brand. He went crazy for the earthborn this morning. I mixed it with his old and he would get a mouth full and run to the rug and drop it and pick out the new. He left the old. Lol.
Anyone feed earthborn or know something better for my Milo?