dying kittens

Question
I have a real problem here,out of two litters of six each, i have two kitten's left and they don't die as little kitten's, the first to die was a six month old male, the second and third were four month's old and so on,all have been big kitty's i had them to the vet had blood drawn and x=rays and they found nothing,i have been a persian breeder for 10 year's and have never had this problem before,the cat's are PKD. neg flv, neg  fip neg,can you give me some idea of what is going on here? i am at my wit's end...any advise would be hreatly appreciated
                        Sandy

Answer
It seems to me that if there are no blood problems at all, you might check their organs. There may be a genetic flaw which is causing their premature deaths. Have you had any of the dead animals given a postmortem? If not, that is definitely the way to go.
If there are no clues in that, then I am also at a loss to help.

Good luck,
Barb