So it's 2 fish effected. I missed that.
Based on what I see in the pics they look like wounds. It's a relatively new setup, with new fish and lots of hardscape. Who knows. You treated with an anti-parasitic and followed the directions 100%? If nothing happened it's either a super bug or it wasn't a bug at all. You just have to watch the meds because dosing too much, too often can lead to liver damage, etc.
I'd watch all fish carefully. If you've got a hospital tank, you could place the two effected in that for now, but I hate to do that with corys given 1-2 of them seems to stress them out more.
Few more days for Petco's $1/gal sale.. Aqueon tanks. Get you a nice 20L or 29.. Just sayin'. LOL