
I have had a bitch with a litter of 9 and hardly any visible milk. Teh idea is that the bitch will have the amount of milk the pups will need, so as long as they are content and gaining well then don't worry.
If you are giving her a complete dry food then you could do what I do to ensure plenty of liquid intake, I soak the food in as much water as it will take, and feed at6 least 4 times a day.
For my 20kg bitches I also give a half pint a day of pupy milk, so expect 1/4 pint would be fine for yours.
I use Nutrolac which is made out of Goats milk rather than cows milk, and it doesn't cause mum or pups any problems, whereas some of the cos milk based formulas have made them loose at some point.