She can reabsorb fetuses doesn't happen very often but happens sometimes, if she was stressed or another reason, also if buck was much bigger she can have difficulties as babies can be too big for her they can stuck etc. If you feel she's having difficulties and your buck is bigger breed as you say he's still young so maybe not his full size now I would suggest to contact your vet. But it is good that her poos are excellent and a lot.
Make sure you refill her bottle before going to bed so she has plenty of water.
Make sure you refill her bottle before going to bed so she has plenty of water.