I also have 2 small dogs, both puggles, and both female. They also had discharge once and metal smell. I learned it was anal glands, yuck I know, but after learning now I know what to look for. Could it be this? Idk, just a thought. I hope all is ok now.
It sounds to me like puppy vaginitis. This is fairly common in female puppies between the ages of about six weeks and 8 months of age. Sometimes it occurs off and on and in other cases it can persist for a couple of months at a time. The main symptom is a cloudy, sticky whitish/yellowish discharge.
While your basic puppy vaginitis is of no concern other than being a nuisance to the owner, there ARE other things that can cause these same symptoms, so it would be best for you to make an appointment with your veterinarian to have a definitive diagnosis made. Because of your puppy's age, though, I wouldn't get too worked up over the potential diagnosis, however it's still best to play it safe and let a professional look at it. Please post back and let us know what the vet says.
Ghilly
When you say "sometimes"...how many times has this happened? And for how long?
How is she in herself? Healthy, energetic, eating well, etc? I think that if the discharge is yellowish then that could be a sign of infection. To be on the safe side you need to consult your vet.