Some bitches do just do this, does the mum see the pups being fed at all? Is it possible to put a few bowls of food down for the pups and also feed mum next to them with a bowl of feed too?
You may feed completely dry at this age, a lot of breeds will eat it if the pups are running in to pinch mum's dry food then just put a couple of bowls of dry down for them too, are you also giving them chicken and mince with rice and scrambled egg? They need a variation of tastes and textures, if you feed these with mum too, (stand and supervise so mum does not steal the pups too) that way she will not feel the need to regurgitate her food as she knows they are eating other foods.
Whenever one of my mum's bitches had a litter, the Alpha female would also go near the whelping area and regurgitate too.

Not sure which breed you have, but aswell as feeding my bitch with her pups I also give her raw chicken wings which she takes into the pups, (of course you must supervise this) so she feels she is feeding them without regurgitation, (even though for the first few weeks they just looked at them, and I secretely removed them, but later on they loved scoffing them down too. :-D)