From what i've heard, cory's are more inscectivores than herbivores, prefer meaty foods such as flakes, crisps and live foods such as daphnia or brine shrimp. They will eat the hikari wafers if it takes their fancy, but they're not really their favourite food. I use the tetra variety wafers on mine and they go crazy for them.
Edit - Just thought, they only have small mouths, if they can't eat the food when it's solid, they probably wouldn't bother when it's soft, although they may well polish it off overnight while your sleeping!