
It might be a good idea, to counter the antibiotics going into mum, to give her and her puppies a little natural yogurt - if you can find goats yog. so much the better. Even at only 8 days, you can put a small amount of yogurt on their tongues.
Hopefully your vet will get back to you asap. and the puppies will be okay. It could be that you may need to bottle them, using something like Esbilac and see if this stops but if she has Mastitis, it's really best they continue to suckle on the other teats. I can't remember, but I don't think the one we had with Mastitis was given antibiotics - just warm compresses to get the teat cleared and working again.
Another thought - did you walk your bitch into the vet's office if she went in, and even more, did you wipe her feet and teats with diluted antiseptic before putting her back with the puppies?