
Hi sholmes78 :)
What a shame for your puppy and you that you're having to deal with these problems. I must admit I think it's a disgrace that a breeder would allow a puppy to go to it's new home with an existing health issue - even on the assumption that it was a flea problem the least the breeder should have done was to retain the puppy until the problem had been cleared :(
However, what's done is done. I'm glad you've moved swiftly for vet intervention and hope the test results are back soon so that you have a better idea of what you're dealing with.
On the subject of feeding the minced beef, I would discontinue
all other foods from the pup's diet except the JWB duck that you've decided on. That includes feeding of treats, chews, table scraps, the crust off your toast or dregs of your tea :) If it is an allergic reaction then the least number of ingredients given the better.
Also check on possible environmental allergens such as carpet and hard floor cleaners, washing powder etc - although the puppy had these symptoms when at the breeder's also, it is possible that some of the same products were/are used by both of you.
HTH, best wishes Teri :)