How is your alk/ca/mg ? How much does your PH change overnight? How much is your ALK/CA fluctating.
Your coral growth (monti in particular) looks odd. I have the same coral, mind grows nice thick branches with bushy ends. When its stops growing its almost always low CA/ALK.
As for the algae, its just normal algae attaching to dead coral, I think this is simply a symptom of the problem, not the problem itself.
Skimming enough? How much skimmate you pulling?
One other thing could be, are you starving your tank of nutrients? I was reading a while back that your not feeding much at the moment? Maybee try and amp up the feeding for 2 weeks see what happens. Screw the phosphate, leave that for Layton to argue about, load the tank with food, cyclops 3-5 times a day, see if it makes any difference.
Are you dosing anything (i've seen people latley dosing strontium, remember its a poison DONT DO IT!). If you are, STOP.
As for comments about you changing lots, I was under the impression you change things with your tank far more than 1 once every 3 months, but I havn't been watching that closley. The advice given was good, take it slowly, stop tinkering and let it take care of it self.
Good luck with it!