sick Red Cap

[BigE94]

Hello, I have 2 grown Red Cap orandas and a baby one in a 36 gal tank with a fluval 205 canister filter. The 2 grown lived in my pond since the spring and I brought them in about 2 months ago. 1 of the grown has been showing signs of swim bladder disease. Cant control his ascent/descent, and sometimes lays on his side, looks like a cork shooting to the top. Ive tried starving him for 3 days at a time at giving him peas, but as soon as I feed him again, within an hour hes back to the top again. They all were in there during the cycle process, and were exposed to some ugly numbers, but now after numerous pwc's the water is as follows..
PH 6.8-7
Ammonia- next to 0
Nitrites- .25
Nitrates- 0
Temp around 70 degrees
I use the API Master test kit.
I dont know what else to do, it stresses him out and I fear Im going to lose this fish if I cant get it under control.