I went through this with Mandi when I first brought her home. I had her checked for worms and it came back fine. The breeder was cooking for the dogs. By cooking I mean the dogs got steak and veggies and all sorts of things mixed in with their kibble. I dont cook like that very often for my human family, so I was having a hard time thinking of cooking for the dog. I decided to give her wet puppy food mixed in with her kibble to entice her to eat.
She got diahrrea.
So I took her off the canned food and mixed in the rice with her regular food and everything returned to normal. So I brought back in the canned food.
She got diahrrea.
I took her back to the vet, who wormed her again, just in case, but still said she had no parasite. I asked if it could be the canned food and the vet said it might be, but that as long as I am mixing it with kibble it should be ok.
Well, I am sometimes a slow learner, so I gave her some canned food again and wouldn't you know it - that puppy got diahrrea again.
She has not had canned food for 2 weeks now. She also has not had diahrrea for 2 weeks now. I think she may just have a sensitive tummy to it. It may sound silly, but it might be worth a try to take away the canned food and see what happens over a few days time.
Now I mix in gravy with her kibble and sometimes table scraps (I know!! Bad mommy with the table scraps, but I am careful about what table scraps I mix in with her food and besides, I am a softy. She convinces me she REALLY wants the sausage or the beef or the peaches and pears and boy oh boy does she LOVE green beans!).
As long as she does not get canned dog food, she seems to do fine.