I've always been led to believe that die-off such as this (when the dead coral is greenish) is usually caused by the wicking of phosphates up into the stem. I find that hard to believe in this instance as the LR is less than two years old. I'm thinking this is simply an example of too little light underneath the piece and the boring (?) algae is secondary. I'm planning to combat this by painting gel at the die-off line rather than fragging the coral at this point. Your thoughts would be appreciated.