
Check the pups nails.
Mums milk will still be main source of nourishment until at least 4 weeks, by five weeks Mums will be cutting back (unless they are like my Myka who loves being a Mum that she doesn't cut them back until 6 weeks and still giving good feeds until 7 weeks).
Most of mien will still give the odd comfort suckle to the time they leave for new homes.
I have them on four meals a day after the first day or two of tasters. This way they will get enough whatever Mum does.
Mum should have as much access to pups as she wants. I keep her away from them for maybe half an hour before I feed them, give more food than they are likely to eat, and then let Mum finish off, and pups will top up from her at the same time.