It is not terribly uncommon to lose 1 or 2 in a litter and it is completely possible that there will not be a runt.If one is it will be smaller than the rest, however runts can thrive too!
Hay is not a requirement in a rabbits diet so long as they are being fed a commercial rabbit pellet that is a complete diet.
Requirements for feeding a rabbit are pellets (complete diet) and water, my rabbits get hay as a treat as well as the occasional lettuce, carrot or celery.