I had a big sps crash last spring, never sorted out the exact cause. Within 3 days, I lost almost every single sps I had. I fragged and saved a few (montipora, birds nest, and one of the acros). I fragged many more that were already too far gone. It's worth trying. FWIW, I also moved every sps into another system so the water change probably have played a big a role as the fragging.