@HiImSean: Three potential issues that I can see based on my experiences:
1. I would get your specific gravity up to 1.025 - 1.026. IME nothing good ever happens to SPS corals below 1.025.
2. I was told a long time ago that SPS prefer dKH closer to 9.0 than numbers above 10.0 (I used to keep mine between 10.5 - 11.0). I used to think a dKH above 10 with Ca in the 450+ range would help speed up growth. That may have been true in theory. However, I have found far fewer problems with a dKH between 9.0 - 9.5. That could just be that my parameters require far less tinkering then when I was trying to keep the dKH above 10.5 and are therefore more stable when I target 9.0 - 9.5. Either way, I have fewer problems at 9.0 - 9.5. It could be your frequent water changes are pushing your dKH higher as well.
3. What kind of lighting are you using, how many watts per gallon do you have, and when was the last time you changed your bulbs? Anytime more than one SPS that has been doing well starts to pale in my tank, I start thinking my MH bulbs need to be changed. If you read this month's ReefKeeping Tank of the Month article online, Reefsmac talks about similar deterioration when his LED's started to reach their end of life. If your montis have been happy for months and are now losing color and polyp extension, your lighting spectrum many be changing due to the age of your bulbs. I have a couple of monti caps at the top of my tank that will actually start to pale and then brown when my 20K Radiums begin to reach their end of life. I'm told as Radiums age their light spectrum shifts from blue to more red, which in my tank is always indicated by increasing amounts of green algae showing up on the glass in my display tank, but not in my refugium.
Your issue may be a "totality of the circumstances" problem where the salinity, dKH, and lighting may all three be contributing to the issue. Make small changes and be patient waiting for positive results. They may take weeks/months.
Good luck.
