Last week, I had noticed a few of my sps corals are bleaching. I have a blue tip staghorn and a green acropora, both show heavy bleaching. I thought it had something to do with the water, so I tested it. Everything is normal. None of the other corals show any signs of bleaching. Then I noticed my colt coral had died, so I quickly removed that before it had released, if any, toxins in the water. I already did a 20% water change. This is the first troubles I had with SPS in the last year and a half. I cant remember how old my metal halide bulbs are, but could that have an affect on it? Like could the temperature color have an major affect like that? I dont know whats going on. Its frustrating too.