Can you please provide more information so we can more accurately help you...
What size is the tank?
What other fish are in there? (please include all species and how many of each)
What are the water params for ammonia, nitrite, nitrate, pH?
Do you have a quarantine tank?
How often are you doing water changes? How much water each time?
Are you adding salt to the water? If so, how much and how often?
What foods are you offering? How much/how often?
Are there live plants in the tank?
How long has the tank been set up?
How long after set up were the fish added? Were they added all at once?
The more information you can provide the faster someone can help you. Most important are going to be the water params (exact numbers and tested before a water change, never after) and a list of all of the animals in the tank. I can't prescribe medication safely without knowing what fish will be exposed to it.
Clear photos also help a lot.