first off-the best way to treat diseases is to first provide a healthy environment for your critters-don't take this the wrong way :wink: -but your basic parameters and maintenance are really lacking here.
the first thing i'd suggest is get a good book, so you can get a firm grasp on the basic environment desirable for your tank.
skimming is NOT a substitute for water changes, regular maintenance,and is not a magic bullet that relieves you from the basic care of the tank!
if the environment is not corrected, all the treatments in the world won't help you.
i'd suggest you start with a few good water changes of 20% weekly(even twice a week!)with mixed, aged (24hrs. min.)new salt water, to bring the environmental levels back to where they should be:
s.g.-1.023-1.025
pH 8.2-8.4
ammonia-0
nitrite-0
nitrate <5
Po4-as close to zero as possible.
i can assure you that your corals did not die of old age! but rather improper care-please make sure you can meet their requirements(lighting,Ca levels, etc.) before purchasing any more.no offense, but it does appear that you aren't aware of their requirements.
it's good that you are asking for info-folk here will try to help(no intent on being condescending, or patronizing :wink: )
before you treat for anything-you should be sure that you know exactly what you are treating for.what symptoms do the fishes have?
fwiw-fishes immune systems function more poorly in a poor environment. water changes alone will help them out.also-most medications are not coral safe, and your skimmer will also remove them from the tank.
HTH
