Sounds like you need to start doing some extra feeding. If the pup isn't growing much at all it's vital you act fast or you may loose the pup. Have you checked to make sure the pup doesn't have a cleft palate?
Also, a photo of the pups together will give me a better idea of how much of a size difference there is. Sometimes the runts are just naturally smaller than the rest. If you are able to get a photo that would be great.
Also, a photo of the pups together will give me a better idea of how much of a size difference there is. Sometimes the runts are just naturally smaller than the rest. If you are able to get a photo that would be great.
Cute puppies! I do see what you mean, she is smaller and looks a lot less developed than the others. Good on making sure she gets her fill when group nursing. Have you been bottle feeding at all? Checking for a cleft is easy, just turn the pup on it's back and look at the roof of her mouth. A cleft often looks like this: 
