[rlcline76]

I am concerned about these black spots, my offhand guess ia a bacterial infection. I like doping my fish elsewhere if at all possible. Less risky to your other critters. I would set up a QT, cheap 10 gallon set up from Walmart. See where the BS is coming from. If your fish can survive a few weeks in QT without signs of illness, then start focusing on the main tank. Could be that you fish were nursing wounds from something in the tank. Could be that one fish introduced something nasty and all of your fish caught it.