SPS problems

[bullit67]

Temps are fine it runs a high of 82 with all the lights on and down to 78-79 at night.
I am dosing 15 ml of spur2 once per week it is a 400 gallon system.
all mushrooms are doing fantastic ric's are doing well getting good coraline growth my pink tip eligance is as big as ever some of my sps are not doing too bad and others are still alive but going brown the ones that die seam to be going through a slow painful death it takes about a week or two.the corals get feed with zeo coral vitalizer every night.