I would think if the fry are different age then eggs then they are eating.
I have seen parents chew up food and pass it to their fry through their gills.
Try feeding the parents small soft food.
If you want to target feed just use a syringe and rigid tube to extend it if needed. Go easy on it though.
Watch for over feeding the microworms, they can overtake fry if they are in a large enough group on bottom of tank.They don't die quick enough like BBS.
I have noticed that freshwater breeders feed salt water foods[BBS] and marine keepers feed freshwater foods [rotifers].
2 lines of thought on this ;
1 each will die in time in the water and not become a pest or permanent tenant.
2 Most breeders believe there is less bad bacteria or passable pathogens since the bacteria the food comes from will also die in the fry tank.