I had half a large colony RTN overnight on me the other day. Nothing new in the tank, no temp swings, no alk swings. The weirdest thing. Don't kill your roommate until you have to :razz:

Already found tem a nice shelf. These things came from 2" frags and grew in this tank so I think it's only fair they get a good resting spot next to the tank

I would take the water to get tested to see if there is a spike in anything (which could be do to an "unexplained" dose).

After the water changes, you may want bite the bullet and cut off the dying parts of the sps the remaining healthy sps to save them.

How high do you keep your alkalinity? High alkalinity and low level of nitrates and phosphates can cause this.

It is a risk to keep alkalinity high. What about copper? have you tested for this? could be in the fish food?

Every spring I notice an increase in posts about SPS death. I suspect pollen.

I thought it was bunnies.

(sorry to joke it totally sucks what happened)