I also have a leather coral that is so old I can't even imagine when I got it. It is not looking to good and is kind of leaning over. I am not concerned about this because this is normal coral wars and they come in cycles. Something in the tank is exuding a substance that the leather coral does not like. The other corals including the LPS and SPS seem very healthy and healthy corals hate other corals, especially corals of a different family. When a coral dies and we don't know the cause we usually blame water parameters, temperature, Lady GaGa, Rap music, global warming, the hole in the Ozone layer or Al Gore. I think it is a combination of all of those things including coral wars. Having a coral war is kind of a good thing because only healthy corals can start a war.
It's like when we see algae. Many people, especially Noobs will say OMG what can I add, how much water should I change, what type of snail should I put in or what is the best church to go to and what is the most potent prayer I can say to eliminate it. Experienced aquarists realize algae is a good thing (in moderation) and grows on every healthy reef in the sea. It probably grows on those under ice seas on the moons of Jupiter but I am speculation and would have to ask Al Gore.