Hiya,
Can you post a photo or a video of the fish, please.
Also, can you give your water stats - current ammonia, nitrite, nitrate levels, plus the pH. What size is the tank (dimensions and capacity), how long has it been set up, how did you cycle the filter, what else is in the tank (animals, plants, decor), how often and by how much do you change water?
All this info helps the rest of us to build a picture of what is going on in your tank.