Hi, I'm new here and I have a 20-gal saltwater tank. one day I spotted some black spots and it started to spread. I went to my local fish store for advice, but he could not identify it. now it's starting to get out of hand and i have no idea what it is. it's not a slim or Ciano. I have a clown fish a Pj cardinal and exquisite fire fish Aswell as a toadstool, I need help and help fast.