Cories are dying

[kllsoul]

About a year ago I set up a 55 gallon tank and it took the whole summer but the tank finally leveled out and has been good. Until about 3 weeks ago. It had 2 fire mouths, 5 rainbows, 4 clown loaches, and 5 cories. 1 of the loaches and 1 of the cories were about 8-10 years old, from an existing tank.
So when one of the cories died, I just figured it was the older one. But I’ve lost 2 more since then. The water tests are perfect, temp is level, and everyone else is doing fine. They keep surfacing like they lack oxygen but the filter alone should be enough and it has 2 air stones. Nothing has changed that I can tell except some of the plant life recently was destroyed by the fire mouth. I’ve put off replacing it since I have to move the tank when renovations are done in my dining room.
Any ideas?

 

[fisman]

Is this a new fish tank that you just bought?

 

[kllsoul]

Is this a new fish tank that you just bought?

No, I’ve had it for about a year now.

 

[fisman]

Can you send a picture? It might be too much oxygen in the tank.

 

[kllsoul]

Can you send a picture? It might be too much oxygen in the tank.

 

[fisman]

To hard to see. Could you give me some information on what their eyes look like?

 

[fisman]

Also, what's the temp?

 

[kllsoul]

To hard to see. Could you give me some information on what their eyes look like?

Eyes look normal. Temp is 82-84 which I know is a bit warm for them but it’s been that way since Sept after our ich outbreak.
I don’t know if these closer pics help.

 

[fisman]

They help a ton more. Does there look like a film on the top of the water?

 

[kllsoul]

No film. Slight algae build in the front from the filter that I have to scrub off again but no worse then normal when I notice it and scrub it.

 

[fisman]

I don't know what this is then. This doesn't look like fin rot. It also doesn't look like bubble disease. I have seen this before with some of my fish. It never turned out well though. Never actually figured out what this disease was though. I will try and do a little bit of research for you though. Hope they survive though.

 

[fisman]

All my tanks have a little bit of algae on the filter so I wouldn't worry about that.

 

[kllsoul]

Thank you for helping. That’s why I’m stumped, I’ve just never seen it like this before. I’ll keep researching too.

 

[fisman]

Hope we can find what the cause of this is.

 

[fisman]

Wait a second I was doing more research and it is fin rot. I'm pretty sure. Can you describe what the white on their tails looks like.