Pale Area On Cardinal Tetra

[BettaBoysGirl]

I check my fish on a regular basis. This morning, all fish seemed happy, healthy, and normal. The only oddity is a cardinal tetra was messing. After tearing the tank/filters apart, I could not locate him. I gave up. Then 6 hours later (cardinal still missing) I find this. Its a pale spot right in the very center of my fish. Its not fuzzy, it simply looks like he lost all his color, but I have no idea why. Hes not swimming right, and I dont think he will last much longer. He is quaritined right now. Any ideas as to what this is?
My tank currently has 6 cardinal tetras, 4 Julii Corydoras, and 6 guppies. Its a 20 gallon long, with 7 small java ferns (clippings from the adult plants that I bunched up), 4 large java ferns, 2 anbuias Nanas, and a medium size batch of jacva moss. There is also drift wood and some plastic plants and decor. Now, I was dealing with Ich with these little guys and turned the temperature up, rather then treating it with chemicals. I took my time, making it a two day process. THe Tetras have been in there just over a week. My ammonia is 0, nirtite is 0, and nitrate is 5-10 ppm. Ph is 7.8. Temperature is currently 84ºf. Everyone was feeding alright. So I have no idea whats goin on. I did do a 30% water change, and gravel vaccum two days ago due to brown algae. I added a pic, let me know what you thing might be the issue.

 

[orangefish]

This is just a guess, but it looks similar to neon tetra disease. I just wondered if you could get a similar thing for cardinals?

 

[BettaBoysGirl]

I was under the impression that cardinal tetras have a natural resistence to neon tetra disease. Its why I chose to go with them.

 

[Ryefish]

is he quarantined in the breeding trap pictured about or is he in a completely seperate water space?