Sorry to hear of your trouble- I think it makes it harder on us with a small litter like that, because we naturally want them all to make it, and it is such a blow to lose one.
I have three litters right now, and have noticed a couple weaker ones. I am going to just let nature take its course and see how they do. The last thing I want to do is breed a lack of thrift into my herd. Sadly, I have noticed that it is my brokens that seem to be the weaker kits and are first to go.
I did try to save Feather's last litter because I believe it was a milk production issue on her end, since none of the kits ever appeared fed. Out of 8, I have two. Now I am unsure what the future holds for them- are they the strongest kits and therefore merit being bred, or just the lucky ones out of a poor litter? They both have Astrex coats, with the doe's being the most extreme, so I'd love to have them in my Astrex program... and they are super sweet from all the handling, so I know my heart will try to overcome common sense.
I have noticed in cats that milk production is highest in the teats near the groin, and less as you move toward the front legs. Does anyone know if this holds true for rabbits as well?