I'm no expert, Lola is on a commercially available raw diet and we only give her one protein due to her allergies. I think once the puppy is accustomed to one protein (meaning hard poops, no allergies), then you can introduce another. In the world of kibble, we wait 1-2 months before deciding whether to switch to a different food or not. I'm not sure whether you should do organs before a second protein though, again I feed raw commercial which has everything already in it. More will be along to give better info. Is there any information on the darwin website that suggests that you can interchange the proteins at will (normally you can do this with raw anyways). It's just hard to see what the dog's reaction will be if too many things are introduced at once, without a baseline of what 'normal' is.