Looks like a bad case of velvet. If not treated effectively, will take these fish down one by one. For me. it is a feared pathogen with a reputation for being capable of wiping out an entire fish population in just a matter of days, in fact faster than ich.
Velvet spores will usually invade the gills first and then kill the fish right then due to asphyxiation. If this happens, you may never see physical evidence of velvet on the skin & fins.
Symptoms include:
- Reduced or complete loss of appetite
- Heavy breathing, rubbing, flashing, head twitching, erratic swimming behavior
- Swimming into the flow of a powerhead which is unique to velvet
- Acting reclusive as velvet causes fish to be sensitive to light
Ive had super good luck using Polyp Lab MEDIC for treament. Also good is Chloroquine phosphate for velvet, but copper also works if symptoms are caught early on. These also work on ich, so if in doubt . . . treating with Copper Power or copper will have you covered both ways.
I would follow Jay's recommendations on 30 day treatment. Also consider fallow with your tank.