I think I would be scared too, to go back to the same breeding. Just because you can't know for sure, if its gentic, or not.
It would take more pups having the same problem, to know if it is. And thats to much heartache to bear.
Was this a first litter between the two, or was it a repeat breeding? Only asking, because it would give you a better gauge.
And only if all the puppy buyers stayed in touch with the breeder.
I'm so very sorry your going through this. Along with suffering the loss, there will always be questions, that don't have answers. The what ifs, and why's that we never get to understand.
Not all those who wander are lost.
Life is just a leap of faith.
Spread your arms and hold your breath and always trust your cape.
Two things define you. Your patience when you have nothing, and your attitude when you have everything.