Did you change his food over suddenly?
As some dogs are more sensitive than others and it's always advisable to change food gradually to avoid upset tummies.
The way to change diet is to gradually reduce one and increase the other mixing them in the same bowl.

Just to add I don't really like either of those brands, they have to many artificial ingredients for my liking. I feed Burns or Nature diet and would recommend them to anyone.

__________________


A dog Possesses Beauty without Vanity,Strength without Insolence, Courage without Ferocity, And all the Virtues of Man without his Vices.