I certainly would. I have nothing to contribute to this thread (except my sympathy and prayers), but I would inform the breeder of ANY finding that might affect her other birds. From what I'm reading here, it is hard to say where it came from or if it is really there (because of your comment from the vet about positive tests). If I were the breeder, I'd certainly want to know about the possibility. If the breeder is unscrupulous, if won't matter to her, but if she is honest, she'll want to "be advised."