hmm, do you feel your non-sps corals are looking off as well? I see you have mostly softies/lps etc. SPS are typically more tolerant of a cleaner system than a lot of the other corals you have in that tank. Your system is pretty mature, and for the amount of fish you have does sound light you aren't feeding as heavy as you could get away with. If all your other corals are fine and it's only your SPS (Acros or ??) I'd be looking at what other things might be fluctuating that might impact your more sensitive corals. I'd also be auditing my equipment if you haven't recently who knows what might be awry after 10 years. Your tank doesn't have that sterile starved look to it at all. Are you running carbon? Do you see things "perk up" when you water change? At 10 years old what have you done so far to combat OTS. Could it be time for some new bac, replace a little rock, etc?