Hey dude, welcome to 3reef. Ok, so you're having some problems, let's see what we can do... first, have you treated your fish for ich? if you haven't, try that, if your fish have white tiny dots/spots on them, it's a sign of ich, very common desease in fresh water fish. Never under any circumstances do a full water change, you'll be killing all your bacteria. How often do you do water changes? and how much?You are supposed to do a 20% water change every two weeks, change carbon cartridges, vacum gravel and scrape glass/acrylic. Now that you have done the full water change, I suggest you buy some bacteria and add it to the tank, check for ammonia and if it's high, which I'm sure will be due to the full water change, plush fish waste, etc, I suggest you buy Ammonia Detox, or any other you might have in your area. Also google for "fungus" and "ich", do a comparison and act accordingly. Do not worry, your fish will survive if you give them the right medication. I think it's ich. But without pictures is hard to tell. | 
