If there is any fighting going on chances are that it is at night.
Your ammonia levels are low but how are your nitrite levels?
How's the tank PH? Has it changed or fluctuated? Have you tested your tap PH?
In relation to the other cichlids where does he measure up size wise? Biggest, smallest, middle?
Are there places for him to hide if it does get rough in the tank?
Gasping usually happens when a fish is in some sort of distress. Which makes me think that he is either being roughed up or that he is sick.
If he is sick it could be any of the flollowing:
Ich.
Gill Flukes
This is a quite form a great web site I visit.
Fish will stop eating for many reasons. The food is not suitable, major stress, fighting and territorial disputes, bacterial, sporozoan and parasitic problems, Ammonia too high, pH problems, temperature problems, internal damage. What changed in the tank? Have new fish been added?
Does any of this apply?
I know that I am throwing allot of questions at you but, if it helps it is certainly worth it.