tank crash?

[Acrowhora]

I'm in need of some advice.i did my weekly water change yesterday and cleaned my skimmer and whatnot,dose Zeovit additives and that was it.when i checked the tank this morning,the water is cloudy and my corals look calcified,and they seem to be covered in sand.im dumbfounded by this i dipped what frags i could dip in coral revive in hopes that it'll help.