From the sounds of it, you still have ich or something similar. Once you get it in your tank, its really hard to get rid of it, and if your tank has only been for a few months, you are just making it worse. Your tank is still new enough that it wouldnt be a big deal to quarantine all of your fish, trash your sand, dip all of your liverock and put it in a plastic tub with a powerhead, clean out your tank spotless and all equiptment, let it all dry out and start all over again. Except this time, put your new sand in with a single fish, damsels are not my fav to start with cause its a pain to remove them once the rock goes back in. After about 4-5days, dip your liverock again, drain the tub you had the liverock in and wash it out well with untreated tap water so it will kill anything alive left in the tub like free swimming parasites. Dry it out fill it back up with new saltwater remove the rock from the dip and put it back in the tub again for another 4-5 days and repeat the process 2 more times for a total of 3 dips over 15 days. After the 3rd dip, let the rock sit for another 7 days and dip again, this time after dipping, you can put the rock back in your tank. The life cycle of most parasites is 21-28 days. Dipping works great to kill free swimming parasites, no dip in the world will kill the eggs without killing the coral. Yeah I know its a serious pain in the butt, but I am having to do it too cause of the parasitic problems I had. I had parasitic isopods attack my powder brown tang, and the dinoflagelettes (marine velvet) attacked it and then attacked everything else in the tank. So now that tank s fishless and has been for a month, but I am not prepared to remove all the liverock and corals out, but I will be hopefully by next weekend, and then I'll start the process I explained to you. I also had Ich back in Jan of this year and I successfully beat it by using that method as well. I cam up with that after trying several various things and lost all but 2 fish from ich back then. I also have hydrozoan jellies now too, to top everything off. If you have any questions about the my method, ask away, or PM me.