Dying corals

[BT05]

Assuming your water parameters are ok, this could be the result of toxins released by neighboring corals and the gradual buildup over time especially if you house alot of softies.

Also, from the pic it looks like the candycane is sitting too close to the green coral to the right (blasto?). I've read that mussids actually have sweeper tentacles (like most LPS) that are rarely seen but still damaging.

I would distance the new LPS additions far away from any of the other corals and run carbon 24/7 to reduce the toxins. I find that LPS corals take weeks to adjust to a new tank and won't show off fully until a month or so. Try to give them moderate flow to carry away any dead tissue.