Dieing SPS

[Milad]

A few months ago I purchased some SPS from someone. As I was putting one of the SPS pieces in, i dropped it and it broke in a few pieces but I still put most of it back in.

A few weeks goes by and it looked like it was doing fine and then boom, white in one day.

Next SPS that ive had for about 8 months which was around 8inches wide turns white in one day.

Last week, one more of my sps goes white and today another went white.

Any ideas what could be causing it? All of them look like they encrusting at the base, growing at the tips. Could it be because of high calcium? Should I be looking out for some critters? Should I changed my lighting faster (150mh that are almost 2 years old, i know i know)?

Nitrates 0
Phosphates 0
calcium 450
Alk 8.7
K 450