Red Lobo not doing too well

The Red Lobophyllia is slowing losing one of its heads. I turned off the metal halide on the one side to decrease the stress but it looks like the head is a goner. The coral has been in my tank for three years without a problem. There is a nearby Spotted Mushroom that I think is causing a chemical war between the two corals and the Lobo happens to be losing. I cut the mushroom out hoping that would help the Lobo. Only time will tell.