The puppies are in the process of weaning.
Usually at about 3 1/2 to 4 weeks, I introduce the pups to moistened puppy kibble. I wait until their mother hasn't nursed them for awhile and then present it to them. Sometimes they take right to it, and sometimes they sit in it, play in it and basically do everything except eat it for a few days. During this time, the mom has as much access to the pups as she wants. I continue these once or twice daily feedings until momma looks at me and says "they are yours now". And thus, we would begin full fledged weaning.
This particular litter took right to the puppy kibble. First day, they ate it all up. And so I started feeding them every day, twice a day. The moms usually back off at this point and I pick up the slack with feedings. Darbi hasn't backed off much yet. She hasn't regurgitated any food for them (normal for my two girls) and is still spending time in the whelping box and letting them nurse regularly.
I believe in gradual weaning and doing it at mom's pace. It seems Darbi isn't ready to start full-fledged weaning yet, so I will continue with our schedule of daily kibble feedings to get them used to the food. She will tell me when she's ready by throwing up some food for them, or letting them nurse for only short periods before jumping away (those sharp puppy teeth!). She still goes in and lays down and falls asleep with them.
I can't say enough what a great mom she is and raising pups out of her is just too easy.
She'll be ready soon enough though...it's almost time.