I'm quarantining fish for the first time. There are four blue green reef chromis in a ten gallon with a sponge filter. My ammonia level is somewhere between 0 and .25ppm. The fish have been in there for about 5 days and are eating well and hiding but off the bottom. They come out and explore during feeding time. I don't see any signs of ich or any other obvious signs of disease. Two of them seem to be missing some scales and have slightly dark colored fins. Is this a sign of marine velvet? I don't want to start treating with copper until I know for sure what that have, if anything. I have seen some weird stringy white poop. Any other symptoms I should look for to diagnose this? I'll try and get some pictures if I can figure out why all my uploads keep failing. Thanks for helping out a first time reefer!