Yep, im not too sure its my bfs tank that we just moved and so im not too sur eon how it works yet, will call him and get him to check everying but they seem to be quickly dying..Any chance of pictures of the fish?
What are your water parameters? Did you perform a 75%+ emergency water change? That would be my number 1 recommendation at this point. I can’t suggest medication, because I’m not sure what exactly is the issue at this point...
Fish turning black usually indicates a huge ammonia spike. What are your ammonia readings?