Clown fish has brown string poop

[HAPPY-REEF]

My snowflake clown has brown string poop. I look with my white lights to see if it was white but it was all the way brown. And I have seen from other forums that white is a parasite and brown is irritation.
If that's true that's it just irritated then what could I do to change the diet? I feed manly flakes and frozen brine once a day and once a while vitamin M

 

[Sebastiancrab]

Assuming it's not a bug, I would try some live mysis shrimp from LFS.

 

[HAPPY-REEF]

Assuming it's not a bug, I would try some live mysis shrimp from LFS.

I really hope it's not a bug. I had this clown fish Since the begin