Vet asap
First, get her to a vet asap as diarrhea can be deadly for a pup this young! Did you do a gradual switch of 1/4 new to 3/4 old food for 2 days, then 1/2 new to 1/2 old for 2 day, etc. or switch her all at once? When was she checked for worms last? It could be the food is just not going to agree with her, but I would have her vet check for giardia and coccidiosis before I changed food. You might even consider treating her for giardia even if she tests neagative as it can be hard to find and it is pretty common for a pup to come down with it from the stress of moving. If she has diarrhea after treatment, you probably should change foods. Seven wks is too early for a pup to leave its mom and littermates. Did you buy this puppy? How about some pictures! We love puppy pictures.
First, get her to a vet asap as diarrhea can be deadly for a pup this young! Did you do a gradual switch of 1/4 new to 3/4 old food for 2 days, then 1/2 new to 1/2 old for 2 day, etc. or switch her all at once? When was she checked for worms last? It could be the food is just not going to agree with her, but I would have her vet check for giardia and coccidiosis before I changed food. You might even consider treating her for giardia even if she tests neagative as it can be hard to find and it is pretty common for a pup to come down with it from the stress of moving. If she has diarrhea after treatment, you probably should change foods. Seven wks is too early for a pup to leave its mom and littermates. Did you buy this puppy? How about some pictures! We love puppy pictures.