If it were my coral, I'd get some fish or shrimp, remove all hard structures, like bones, exoskeletons, and scales, then cut them in pieces about the size of a pencil eraser, soak it in vitamins and amino acids, and start feeding the coral now. The frequency of feeding will depend on the coral. My goal would be twice a week, but the coral may not feed that often right now. The more nutrition you can get into the coral, the faster its health will improve.