Little discus being weird

[SaMoDiscus]

Hi all. I have a 60gl tank with 6 discus, 30 cardinal tetra, and 4 panda cory. Normal water parameters, I keep it at 86 degrees.

Everything has been fine for 6 months, suddenly the smallest discus 2" started hiding and not eating. Everybody else seems fine. The larger discus 4-5" are displaying breeding signs and are maybe a bit more aggressive. I've been doing daily water changes for a week 50%. Still no change. I got worried bc he wasn't eating and just hit in the crevasse of a rock, so I moved the slightly bigger bullying 3" discus to qt and removed the hiding spots from the main tank. Little guy looks fine, but stays in the corner, making an occasional lap around the tank. He's swimming funny, kinda jerking and bumping into the sides of the tank. Still not eating. Any ideas?

[SaMoDiscus]

Now he is floating on his side at the bottom. Every now and then musters up the energy to awkwardly shoot to the top and sip a bit of air. Not looking good.... Please help.

[nc0gnet0]

You have had these fish for 6 months and one is still 2" and another 3"?

Can you tell me what your wc and feeding routine was prior to this?

-Rick