Saltwater fish have quit eating and have lost two

Question
I have a 110 fish and live rock tank. Have had it up and running for almost a year with no problems.  We check the salinity weekly and with every water change which we do once a month as long as our water test are good. We test for ph Nitrites, nitrates, amonia, calcium, and salinity and all are in thier optimal levels.  My remora is spazing out my live rock is dying, and I have lost my 8 inch lion fish, and fox face tang.  I don't know what else to do. I have a sump with the bio-balls, and a new protien skimmer that is working as far as I can tell please help.

Answer
Hello Heath. From my experience it is very hard to diagnose a problem in a tank without actually being able to see it. However I can offer maybe a few things to check for. First of all what kind of water do you use? It is tap? When you last did your water change did you use water from the same source that you have been? Did you switch salt brands? Did you notice any signs of disease? Scratching, Flicking,rushing around tank,or not able to keep and maintain swimming equilibrium are behavioral signs of disease. Any physical signs like white spots, a powdery look covering the skin, black spots,white patches,cloudy eyes,fins eroding,or a sandpaper appearance? Now you have to look at environmental factors like is it possible that an unknown chemical could have entered the tank? Aerosol sprays, flea powders, bug sprays,certain lotions on your hands,chemicals added to tap water,certain metals,and a huge variety of other things can cause this reaction. If there are no outward signs, and considering your live rock is dying as well I would consider a toxin in the water. Have you tried doing a large partial and replacing any carbon you might have? It is very hard to diagnose over the computer but I hope I have given you some direction to go in.Sorry to hear about the loss.