My tank is a 20L and about 2 months old. Clowns have been in for 3 weeks and are very active. My water is within parameters but I post specifics if it is applicable (I have two shrimp and various snails and another clown that are all normal). I noticed two new brown marks on one of my clown's white stripe headband, that weren't there before. As best as I can tell, it is flat. Should I be concerned? Clown is about 1 inch long. Thanks! I'm super worried about the little guy, this is my first salt tank, but I have done hours research and question asking at my LFS.