If the eggs are on plant leaves then I guess you can't screen them.
Many times, females are the main culprit. I have one pair and the mother eats them as they start free swimming. I remove her after spawning and the dad raised them at first, now he eats or doesn't care for them as well and they die off.
The perfect breeding tank for discus is bare bottom, a single sponge filter and a breeding cone. Even then, some pairs never get it right.