VERY sorry to hear this, I've just lost all three of a litter I was very invested in and I know how much effort goes in to keeping them alive even when it appears they would rather not be....
You fought a good fight and brought us something very interesting. It's sad to hear they didn't make it, but the genetic question is still very valid and I hope eventually their origin is solved.
If it really was sperm retention you may have just discovered the limit of storage viability....