The Corys look starved. Their bodies should be rounded, but not huge. I can tell that they're not getting enough food. Are you feeding them, specifically? Or are you expecting them to glean enough from the bottom to survive? It's best to feed a couple of sinking pellets after lights-out to ensure they get food. Mine eat fine, but I feed frozen food, which sinks quickly. As for the bumps, it looks like fungus to me. Are you keeping them in the right temperature for the species? I'm not saying this is the case, but often Corydoras are sort of added as an afterthought, "cleaner fish", etc., but they need specific care, just like any other fish.
Edit: It's definitely not ich.