Is this newly acquired? How high in the tank was it when you bought it? What type of lighting? Lettuce or Cabbage coral are high light and medium flow corals. They are concidered to be SPS corals. The mucous strings that you see may be normal if it was just introduced in the tank. You want to place this coral mid to high range in the tank, but on a stable area, as not to have the coral fall, resulting in injury. The slime is normal for a newly acquired cabbage. They also use the slime to capture food if not new to the tank.