Help! X-Ray Tetra Strange Behavior and Worms?

[spacemanmax]

Hello! Needing some advice here... had this 50 gal for several years, got it from pals who have had the fish even longer, they are probably 5+ years old. Lately, our smaller X-Ray Tetra, Luke, has been swimming against the bubbles, seemingly playing, but nonstop all day. Now he is sitting at the bottom, not moving much at all. Upon closer examination, he has some black spotted coloration in his stomach, and some fin rot. Looked into Neon Tetra Disease, not sure thats what it is but I'm fairly inexperienced with fish illness. I put some fin + gill medicine in the water and will do a quarter change tomorrow. Also, found tiny red worms, and upon examination found a whole ton of them on the glass. Biggest one I've seen was no bigger than 3cm, best guess is bloodworms but again, inexperienced. Anybody have some advice?

Attached are photos of Luke, the seemingly sick X-Ray, Lorelai, our healthy X-Ray, and the worms.