well I don't have any experiences in keeping discus but in most cichlids it takes several spawns to make a good care taking parents.1st 2nd and sometimes more they may eat their own fry.But You don't have to worry about it,for sure and certain they become good parents later.
They eat fry when they are freeswimming or the wigglers?I don't think they don't eat those wigglers.As soon as possible remove freeswimming fry next time into seperate grow out tank.