
I suppose the question is always how long is a breeder responsible (in terms of a full refund) for those puppies they sell. As a retired breeder, I'd not look at making a full refund after 8 months, after all environment plays perhaps as big a part in how a puppy develops, as do genetics. Were you in contact with these breeders recently? Of course I'd take a puppy back, with a full refund, within weeks of them going to a new home if the buyer wasn't happy with their pup - if only to get that puppy out of that situation and back with me. I would try to make it work - eg asking them to come with the puppy and me, to my vet for an assessment (all my puppies went with an individual health check however). And not to suggest I'd not have concerns if a puppy I'd bred had 'fallen apart' to the extent your youngster apparently now has.
So these people are 'top breeders' - in terms of show success, or quantity!! Of course many bigger breeders will do their litters during the 'closed' main show season but to be doing 3 in a short space of time would have alarm bells ringing for me. And further, did they sell your puppies fully endorsed - good breeders will endorse immature stock, and even more so if they know the owners intend to start breeding. They should retain the option to see the youngsters later on, when closer to breeding age, so they can see whether they have matured into quality animals before lifting the endorsement not to breed, to protect the breed as much as their bloodlines. Hip dysplasia can be diagnosed early on, but not scored.
It's disappointing, obviously and worrying given the figures you may be facing but again stuff happens. I bought, at 4 months, a male from somebody who'd been in my main breed probably longer than I have. I hoped to get back in the ring with him, but apart from the fact that shortly after I bought him home, his stools were so bad that I had a fecal done which showed he had Giardia, and roundworm eggs (despite being assured he'd been at least wormed for that). Further, a few months later he started showing some lameness and full x-rays showed he had premature closure of the growth plates, ulna, both sides. He developed more turn-out in front than I wanted (even with a Basset). I invited his breeder to contribute to the cost of all this - they sent me £100. Hum. If the dog hadn't been such a nice person to live with, I might have returned him - and dickered over a refund than. As it was he wasn't going back and I've had to swallow his ongoing construction problems which have included more x-rays which now, at 8 years, show significant sub-luxation of the hips and a spine that makes me wonder how he's still mobile. He's on Metacam for as long as he will tolerate it.
What you do about your bitch is going to be your decision, but I do question whether you should/can expect a full refund for a bitch you bought as A PUPPY and who 8 months on, has fallen apart. It would be different had you bought her, at a significantly higher price, as a young adult, ready to be bred from. JMO.