SPS dont need a reason to not make it, just being sps is a reason.
Ok, I agree pics would help, esp. giving the acro experts here a look see. I dont agree salinity is a problem, although I would never keep my sps reef at anything under 1.024 -1.025
Magnesium is important with those corals. And its relationship to calcium. If your depending on water changes with IO to keep it up, and unless something has changed, it has low magnesium. I always use IO, but add calcium and magnesium, following Ben,s {chemmaster} formula. Mag. always stays at around 1350 this way.
I would also run a lot more current in an sps based aquarium of that size. My 90 is just softies now and I still run two large Hydors, {1200gph}, two large powerfilters and a Tunze 6080, rated @ 2200gph.