Mysterious bleaching

[dtum]

Last week I have started to see some bleaching in my tank's SPS.

First it was a birdsnest colony that had a bleach spot one evening and then bleached overnight. Another smaller birdsnest the other day.

Yesterday I noticed a few more. What could be it? Most of my corals are doing well. Water parameters are seem okay.

http://tapatalk.imageshack.com/v2/14/09/18/e94b57a26a185fc3e80e8c8622d1594a.jpghttp://tapatalk.imageshack.com/v2/14/09/18/70c964e7a40a2e6f15e0edbfd77a2920.jpghttp://tapatalk.imageshack.com/v2/14/09/18/b760d9e85cc6db74f8b28b5130ec8663.jpg

[PL-Reef]

Water parameters are ok? Could you post them for us? We'd need some more info on your system to better help you. Lighting and it's schedule, WCs, are you running any type of reactors, additives, any big changes recently? It really could be a number of things.

[cugly]

It looks like rtn from the base

[deeznutz1]

Looks like RTN for sure :( I'd clip a few good frags off them.
Did you have a major ALK swing?

Do you any source of carbon?
Did you change any media recently?

I hate this part of the hobby.

-dan

[EuroGTI]

Yea..that's not bleaching. Those corals are loosing tissue. Like others said, I would frag a couple pieces just incase. Stn sucks, good luck!