Discus dark, not eating, shaking one pectoral fin

I'm going to apologize in advance for not copy and pasting but I will give you as much information as I can remember from the questionnaire.
Parameters 0,0,25
Temp 84.2
No new fish or any major changes added in almost a year.
Feed frozen beef heart, spirulina brine
No RO
7.2 PH
hardness 150
Buffer 80
Water changes 50% once or twice a week
Course of General cure almost complete (shot in dark)

Any ideas or advice. Thinking erythromycin treat next. This fish is one of my two breeding pairs he he just spawed less than 2 weeks ago and then this happened. The fen he was shaking does have a small white mark on it I'm not sure what that is. I am absolutely stumped this tank gets absolutely zero changes in routine. I have two breeding pairs in this tank. Attachment 132187Attachment 132188

I figured it out. No replied needed, post may be deleted. Thanks

Sorry for the late reply. Glad you figured it out. It doesn't seem to be anything some additional water changes wouldn't cure...