I would not panic just yet rcon021,
I don't know how many females you have but unless it was the same female the eggs may be old.
just keep breding them .....
I have bronze corys breeding from time to time, unless the same female breeds twice in a short time the eggs have a very poor yeld, so this maybe the problem you are having....your fish are full adults not young adults.
So...just keep doing what you are doing if your fish are fine you will get good eggs in time.
What ever you do don't give up other wise you will go back to square 1.
as for water flow over the eggs, this maybe a problem but remember the fish know what they are doing and will choose the best area's to place there eggs.