The problem subsequently spread to a red snapper (photo) and a mangrove snapper. Two contacts suggested the problem was a bacterial infection secondary to nutritional deficiency. The pomp always looked thin, but the snapper was growing (got most of the food). We were feeding mostly frozen shrimp. We medicated the whole tank with Melafix and started feeding more of other things like Mazuri meal and mullet. Situation seems to have stabilized. Fingers crossed.