no idea, maybe as you say they are quite big,although one pup was very small only half the size
and never thrived,so it was pts,one other is smaller & lighter but real healthy so was kept .
second pup born was stuck sideways in the womb,and her labour stopped,so took her to the vets for a hormone jab and she delivered the rest no probs .
Sorry about the one you lost. I lost one in my litter. I still have a smallest of the litter, but he is healthy and strong if there was something wrong with him he would have died by now. Glad the jab worked for you, didn't for mine. Good lu