i agree with joshua, you alk is way low for sps corals.

sps corals are based upon a few simple things, calcium and carbonate being really important. its nice that you have your calcium level up, but the lack of the buffering capacity of your tankwater needs improvement. your alk level should be around a 7 or 8. by maintianing a higher alk level, you will provide the much needed carbonate for the sps corals.
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