If he has emaciation in the abdomen its likely he has the quite common skinny disease(not the actual disease but a symptom) Malawi's are known to get this, usually its the females that suffer after holding for a long time + without feeding. He needs to be treated and wormed, believe it or not interpets swim bladder/ interpet anti internal bacteria treatment is a great cure for this but he MUST be wormed to, to give him that extra boost (Usually these treatments i find are useless and dont seem to be concentrated enough)