what kinda fish are they? sometimes certain fish will start to do that when you need to do a water change or if they have been stressed out could be alot of different facxtors that cause it but i know when i had my midas and now with my blood parrots that happens and once i do a water change it clears up...
Black spots can be anything from disease to diet to stress to a natural coloration for that species of fish. More information is required before any one of these causes can be attributed to your situation. I will say however that disease is usually not the cause for most people.
Seems like some of my Rusties and now my Iceberg Electric Blue female is starting to get a bit of black. The "spots/flecks" almost looks like what black ink would look like if it was slightly brushed onto the fish. I noticed it in the past on a couple of Rusties and thought that it was maybe just the species and part of the maturation process. However, the same look is now appearing on the otherwise plain looking female Iceberg, so I wondered if it could be problem that I need to be treating.
I am not familiar with those fish. You may want to see if black spots are part of a normal coloration phase for those species. If not, I would wonder if it is spirulina spot (from feeding too much spirulina) or scars from an aggressive tankmate.
I think I have a Orange Midas Cichlid that might be going through this process as we speak. I was thinking that it was some kind of disease and now I am unsure. I've included a pic below. It definitely looks like "Black ink" spots.flecks. I've included a link to a pic below. Any information would be appreciated as this would help me figure out what is going on with my Midas!