
You cannot tell by looking at the bitch whether enough milk is being produced, some never bag up yet have plenty.
Only the pups weight will tell you. Milk is based on supply and demand, so if you start supplementing less will be produced, so should only be done in an emergency.
So instead do everything you can to encourage the bitches liquid intake, space meals regularly through the day keep pups nails short and encourage them to feed almost constantly in the first 3 - 5 days and at least hourly in the first week after that.