Stressed or Dying Corals?

[CoralineCori]

I recently treated our 40gal reef tank for a red algae (cyanobacteria) outbreak that had built over the course of a few weeks. I used Easy-Life brand "Excital Red Algae Remover which was recommended by my LFS. I was told it was completely reef safe and one of the more natural treatments as it promotes the growth of "good" micro-bacteria which smothers the "bad". I treated as directed over the course of 5 days, and sucked out the red algae as it appeared and everything seems to have improved 100%. The downside to this and I'm not sure if it has to do with the treatment or not, is that a few of my corals have declined in health recently. My Pulsing Xenia's although one of the hardiest of softies is now dark pink, shrivelled and the polyps are closed up. I did notice a few tiny pulses from some during feeding but barely readable. My Goniopora (flower pot) which was once thriving and had even turned a healthy brown on the tips (sign of good health rather than being bleached) is now receding into it's skeleton and is hit and miss with extending. Only the green Zoa's out of my mixed red and green are opening up and the red are closed up tight and have beeb for a week. Also my rose bubbletip anemone decided he wanted to vacate his usual spot and hide behind the rock and only come out for a bit before feeding before deflating. All other corals in the tank (purple, red and brown mush, clove polyps, pink Zoa's, Hammer, Acropora, Montipora and Duncans) are still doing great as well as fish and inverts. The tank is well established over 2 yrs, we do weekly 5 gal water changes, we have ONLY ever used R/O water, run UV sterilizer, protein skimmer, canister filter with all media except for when treating water, feed both fish and corals a wide variety of food every other day, use additives only when needed such as: Prodibio Bioreef kit twice a month, Prime water conditioner, Aqua Vitro brand 8.4 buffer and calcification and have cut back our 2 dual aqualife T5 HO's to 8 hrs. The only thing we did change was the salt which is still same brand (Instant Ocean) but we switched from regular marine salt to reef salt. I am at complete loss of what is going on other than maybe it's just time for these corals to kick it. We closely monitor our water params and everything has always been good and consistent other than our higher reading of calcium recently. I will list the water params here:

NH3/NH4 - 0
NO3 - 0
NO4 - <3mg/L
pH - 8.3
Ca - 550 (higher than usual)
dKH - 8.5 or 150mg/L
PO4 - 0
Salinity (SG) - 1.025

Any help with suggestions or reasons why these once thriving corals are hardly lively anymore would be greatly appreciated. I am running out of explanations as we are doing everything we that we possibly can.

Thank you!!