you need to feed her extra. she needs to have foods high in calcium and protein. I give a half boiled egg and two tablespoons of cottage cheese twice a day. I stand them, on top of the washer while they eat it, so the others don't get it, or put the other one in another room, or outside while she eats.
DO NOT give calcium, supplement while she is pregnant, you can give them to her after she whelps.
How much did she weigh before she was bred.?
Please go to this site and learn all you can to prepare yourself for the whelping.
Dog Breeding and Canine Reproduction by Debbie Jensen. Dog Breeding and Whelping guide for dog breeders.