Check the water conditions daily. If some of the discus are eating and some are not, put the ones that are not eating in a separate tank and medicate. If, during the 24 hours, the fish show signs of stress, do not panic. Some signs of stress are clamped fins, shaking, scratching, shimmying, heavy breathing, and a dark or black color. If this happens, first check your water conditions.
Poor water can cause stress.
If the water is ok, try upping the temperature to 90 degrees for 24 hours. The higher temperature may cause heavy breathing, but may help the discus get better. If the discus do not do better after 48 hours, you should contact the seller for further ideas on how to treat them. The seller should be familiar with the discus and have some experience in treating sick fish. In a few weeks, if no medication was needed, the environment of the tank will stabilize.