Fresh veggies are NOT always great. Rats are not fruit or veggie eaters, they are grain and seed eaters. Veggies will actually give the mother diarrhea and prevent her from being able to hold fluids properly, or nurse properly.
Dandelion greens are the only vegetable matter I'd suggest feeding to nursing mothers. One leaf every other day for the first week will increase milk production.
Seeds are good, so is dog food, cat food is okay, but dog food is better.