Wasn't she just fine on the lamb canned alone? I agree. She is very young to keep having an unbalanced diet like this.
She did well on raw lamb?
Well, I'm (of course) not going to say that a vet isn't needed. All puppies with diarrhea for whatever reason should technically be seen. Since this keeps happening, and it has been pretty liquidy, I'd start to be quite concerned about her hydration status even if she looks normal. So I'd say if she starts to look at all dehydrated (even if that is at midnight and you have to go to the ER), then she has to go in. And if she isn't better by morning, then she has to go in. And if she has maybe like more more one bout of this again today, then she has to go in... It's not that I'd be worried about the underlying cause nearly as much as what it is doing to her.
Also, I'm guessing it's just because things keep getting switched, but if the GI problems continue around food, then some testing should be done.
I don't believe a nutritionist would be of help right now. The non board certified won't balance it according to AAFCO and that is way too risky. The board certified are going to stronlgy discourage feeding a pup homecooked food because it's also risky for development. And as far as recommending foods, they will be foods that you don't like...
Lamb as the sole protein source is perfectly fine. You will hear about mixing and rotating and and and. But remember that not all dogs can handle all protein sources. I'd be much more concerned about getting her on something that her stomach agrees with than trying to get several kinds of meats in her diet (which is very debatable anyway).
Hey, my dog does absolutely terrible with meat and even most fish. Right now she eats soy as her protein. Yup, I have a vegan dog. So what... At least it keeps her alive.