Hello shel...
Don't put medications in the tank water, unless you know precisely how they will affect the fish, plants and good bacteria. Unless you have a degree in fish biology, you can't be sure if there's an internal problem. Keep the tank water a little cleaner, by removing and replacing a little more and more often than usual. Feed a little less and add some minced garlic to the menu. Spice World has a very good product. If the fish are a bit under the weather, they tend to eat less and you don't want uneaten food to foul the tank water. The garlic is high nutrient and has natural antibiotics.
B