[Black spot around pleco's eye ?]

Black spot around my pleco's right eye. Seems to be acting normally, eating fine, just showed up one day. It's been over a month, no change. Only one in my community tank. 78deg, ph 7.0, soft water. No ammonia, or nitrites, 30ppm Nitrates.

Tankmates: flame gourami, cory cats, neon, candy cane, Silvertip, rummynose tetras. Few otocinclus..

No idea what this is or if I should  treat with Erythromycin?

[Trying to identify this]

My red shoulder severum seems he has a white stringy thing on top fin of his left side. Not sure if its some sort of parasite. I see other fish that have a tiny white spot near front of top fin, not stringy though. They are eating well, not thinning out, just something I've noticed.Wondering if I should treat with salt, if so , what dosage, or some general cure or erythromycin  or a combo.