Plecs create a lot of poo.  Two Plecs in a 10 IMP gallon with Corys and mollys would seem to me to need frequent water changes for the Cory and some aggressive filtration for the Plecs.  I missed actually how the tank is already stocked.
Corys feed by feeling around in the substrate with their barbells.  I have watched worms escape them easily.  I doubt they would go after your midlevel and top level fry.  It would seem like it would be more unintentional.  I have a pair of guppys breeding in a 29 USG with harlequin Rasaboras, Jari zebra Plecs (an omnivore) and a large number of Corys.  I have not seen any swimming after the fry for a snak.  I have to soon start finding a new situation for the fry as they are multiplying without any help.