I agree with Swack, true runt's of a litter will probably show some health issues very soon after birth. I like yourself for years considered the runt as the smallest of the litter. Back in the 90's I kept the smallest female out of the last litter from my male and female because every body overlooked her. Let me tell ya I ended up selling that pup when she was about 4months old to a buddy of mine and after she was trained up she was by far the best hunting dog out of that litter. I wish I'd kept her myself. What I am getting at is, "don't judge the book by it's cover". That little female ended up weighing what her female littermates weighed and was an excellent gun dog.
" Time is one thing that can never be Retrieved "