Not sure. I thought mine were sick when in fact they were pregnant. Very swollen bellies. My Rosy Barbs weren't eating much (which I again attributed to sickness). That might be one way to tell. Are they still acting normal and swimming all over the tank? Mine hid behind plants in a fairly dense area, I'm guessing because they knew it would be safe there for their babies.
Again. All this was happening when I thought they were sick, so that might not be normal behaviour.