So my tank is finally sorted out and my fish aren't dying. But I woke up to this today. My oldest cory (the one that's stuck with me through everything) is missing scales on a quarter of her body. It looks like her plates are still there, but you can see the muscles underneath. She's also missing a barbel. Her eye looks like it's still there, but it's been hurt too. My phone's camera's focus just makes it look like a pit. I've currently got her hospitalized with a small amount of aquarium salt and some tea tree oil. Dosed a tiny bit of prime too, but used the water from the aquarium, not a new batch. Her other side looks great, just like a cory should. I didn't notice this until she started swimming in spirals. At first I thought maybe she'd burned herself on the heater because it malfunctioned, but other fish are laying on the glass under it just fine. My best guess is that something attacked her in the night. I've heard of ghost shrimp eating betta tails. Would they be able to do something like this? My more plausible theory is that one of the plecos got a hold of her. Is this the kind of damage that can come from a pleco attack? Will it heal? I fully expect her to have a scar. Or would it be more humane to just put her down?