I supplement flake with sinking shrimp pellets. the substrate in this tank is usually clean of ANY uneaten food.
Also, these are shoaling fish, they do way better in quantity vs solo, it will aldo bring more activity out of them with 5 or more. They may or may not be a pair, depending on gender, the females generally have a rounder belly and are generally rounder than the males. Mine started laying eggs after about 8 months or so, cold water triggers the response, as in a spring rainfall.
Have fun watching your cory cats!