I need help. Ever since I did a water change on sunday I have lost two of my mbuna and my catfish! I don't know what I did. It was just a normal water change until I saw the fish becoming sluggish they wouldn't eat and thier colors were fading. I thaught maybe it was because I raised the ph or added salt but I've done this before. Now my synodontis decorus, my socolofi and my biggest red zebra re gone. My other fish seem to be doing fine but that's what I thaught yesterday woke two fish dead. I checked my parameters amonia and nitrite are at zero and nitrate is low. The fish that looks the sickest right now has light white patches all over his body and looks very skinny and weak. It even got sucked by the filter. I thaught it was dead but it swam off. Any ideas of whats going on?!?!?!