Welcome to AC - sorry your first post is about fish death. Can you give the following details :-
1) Tank size.
2) How long set up and if recently how did you cycle ?
3) What filter you are using ?
4) What inhabitants are in the tank ?
5) Anything at all added recently (plant/decor/fish/invert etc.)
6) What's your maintenance regime (how often do you change water and how much do you change. How often do you gravel vac).
7) What water conditioner do you use ?
8) Test the following with a good liquid drop test kit (paper strips useless) and post results : ammonia, nitrite, nitrate. Ph too why not.
Fish gasping at the top of the tank is indeed generally a sign that they are not getting enough Oxygen. 'Organic'/chronic cause can be overstocking the tank, insufficient surface oxygenation. Acute cause can be pollutants, nitrite poisoning. Also, sick fish will often head for the surface/shallows as they are weakened and it is easier for them to breathe up there and in the wild the water is warmer.
Are there any other physical symptoms ? How are their gills ? Any 'cottony' patches/red streaks ?
If you give the info sought above we can start narrowing down the causes and address them. I'll hold the thread here in cichlids pending that - may be you are dealing with a disease isssue, may be a tank issue.