Hey guys new to the saltwater hobby moving from years of fresh water tanks, quick overview of the tank: It's been up about 4 weeks now, 60G tank with overflow to Trigger Systems 30 sump with refuge, 60# live sand 50# dry Fiji rock from BRS. Tank cycled quickly using bio-spire and I've been dosing Kent Purple Tech, I know some people say it's "snake oil" but it's been working great for me as you can see my rocks have some coralline on them, however I have noticed some what looks to be brown spots on my some of the rocks. Can someone ID for me please, is this the start of something bad? I have a cleaner shrimp with 2 turbos and 2 red hermits.