
She will only get more milk if they feed more. Have you cut their nails, as by four day they are often quite sharp.
Is the whelping box too hot for her.
I would make sure she went into the box at least every hour and sit with her plugging pups on and talking soothingly to her.
With my breed that are usually 10 - 12 ounces but often nearer a pound I would be content with 4 ounces in the first week with large pups and an ounce a day with the smaller ones, though would prefer an ounce a day and up to 10 ounces with the smaller ones..
In the second week I would want at least an ounce a day.
The amount of milk or fullness in her mammary glands has no influence on how much milk is actually being produced.
My Lexi id her pups very well, but in her first litter was almost completely smooth underneath, no boobs at all, just larger nipples.