They are so adorable. I just love kittens!

As for their positive tests: I really wouldn't be surprised if they tested negative later, as they are still young enough--as the vet as suggested--that the tests may just be picking up their mother's antibodies. That said, has the mother herself ever been tested? If the kittens picked up something from her in utero then, presumably, she will test positive for either or both disease. I would assume that her test will be conclusive.