Is the puppy one of the litter you bred in August, or is she a puppy that has come to you from elsewhere? The reason for the question is that puppies are prone to stomach upsets when they leave their breeder and go to a new home. It's a time of huge stress for them and it's all too easy for them to be a bit under the weather.
I notice that your post back in August was about the bitch that had just given birth having diarrhoea. Did you take her to the vet as advised? Is there any chance that the pup's diarrhoea could be linked to the problems that the bitch had?
Changing food, eating plants out in the garden and scavenging rubbish or eating toys are also possible causes, as can reactions to vaccinations. But even though your puppy seems well in herself I'd take her to the vet sooner rather than later because she's so young and vulnerable at 11 weeks. Young puppies can easily become dehydrated.
I'd also restrict her food to simple and bland things like scrambled egg (don't add milk), or cooked skinless chicken and rice until you take her to the vet and I'd make sure she kept hydrated.
Hope she's OK soon, and please update us about her
