
Did you worm Mum while she was in whelp for 25 days? I would not want to worm pups this young.
Has Mum eaten anything odd or over rich. Certainly with human babies what Mum eats can affect the milk and the poos.
Is she getting 4+ times her normal rations?
If pups are not gaining well do they seem ready for semi solids assuming their eyes are open?