This problem is nothing near as bas as the Head Down problem - but if your fish are hovering lethargically with heads at the water surface, not gasping, just hanging there  - then Check your pH as soon as you can. This can be a symptom of pH crash which is leading into acidosis. Very often, if the pH is falling rapidly and the fish will hang under the water surface, and also start getting a milky skin. 

It is always good practice and is recommended to follow up with an examination of gill tissue both visually, and microscopically.