What you may be seeing is colostrum. Did you try all her nipples? If the pups had just nursed on her you might not see as much but since there are only two pups I would think she would be full of milk.
You could make her some whelping pudding and that might help bring her milk in better. The pups should have full bellies and they should be nursing every couple of hours.
If they are nursing and not getting enough milk then they will slowly get weaker so I pray they are getting enough.
How Long After the Baby Puppies Are Born Does the Mother Give Milk? | Dog Care - The Daily Puppy