Awww, they are all so precious!!!
I am so sorry you lost a little boy. I would have been so mad at the vet, that is just carelessness on their part and because of it you lost a little boy.
I was thinking the average weight is around 3-5oz when born, but I could be wrong.
I am glad the other puppies are all doing well and gaining weight and glad the mom is doing good as well!!
Keep us updated on their progress!!