HELP!! SPS Dying

[gerrygab]

I have a problem. Over the last eight weeks I have added 3 or 4 sps frags plus a plate coral. They have been shrinking back, turning white and dying.
I will tell you about my system, some of which is old tecnology. 90 gallon 100 lbs of base rock, amiracle dls sump, Sieo 820, Tunze 6060, rowaphos and a reactor, 2x 250 watt 13k Giesemann bulbs and finially a Via-aqua canister filter. Now, my water test is Temp 81, Cal, 475, Alk, 7.2, PH 8, Sal 1.024, KH 2.55 and Nitate 25. I think the big problem is Nitrate levels. My plan is to get rid of the canister filter and old style drip filter and build a new sump so I can put my new Euro-reef skimmer and make a section for a refugium. Does this sound like a correction to my problem? Oh yeah I'm doing 25% change tomorrow. I know I will get lots of different opinions but I want to know if I am heading in the right direction with the changes. Thanks, Gerry