Help with diagnosis and treatment on Percula

[maxinf]

My water parameters are good and I introduced 2 clownfish on a newly cycled 20Gal tank that was setup a month and half ago. Both are eating well and pretty active, however I noticed this black patch on one of them. Also I noticed white stringy poops:

I have three hypothesis (Parasites, Bacterial Infection or Worms) but I'd like to confirm the diagnosis and treatment. I have available a hospital 15G tank and the some basic meds (Seachem MetroPlex, KanaPlex, NeoPlex and Cupramine).

1. Do I need to treat him, or since he is behaving well I should wait for self recovery? I'm afraid to stress him even further
2. What would be the right treatment, considering the meds I have?
3. Do I need to treat the other clowfish, even if he is 100% well? I have no other tank inhabitans except 2 small zoa frags

Below are some pics:

 

[canadianclownfishguy]

When I receive clowns that are/have been stressed out they tend to have white stringy poops occasionally but they usually clear up quite fast after entering my systems. Is the black patch raised or textured?

 

[maxinf]

Is the black patch raised or textured?

It is definately textured and not raised at all. Also you are right, white stringy poop seems gone now... is it a bacterial infection then?

 

[Jay Hemdal]

Can you get us a picture under white light instead of blue? I just can't make out enough details to hazard a guess.

Jay