That really does sound like some sort of allergic reaction or reaction to a bad batch of serum. I would definitely go to another vet to get another opinion and possibly a checkup to make sure the dogs are alright. I've also heard that as of late, some sorts of shots that have been given yearly are given too often(maybe only needed once every three years) and have caused sarcomas to develope in dogs and cats. Kinda off the subject there, but it's something to look out for when getting shots administered. Also, giving them in different places each time will decrease the possibility of getting sarcomas.

Let us know how the dogs are doing!!