Bleaching corals

[apstreck]

So I've had a few of my corals start to look bleached out over the last week or two - a hammer and a chalice. There is also a mushroom that looks shriveled up. Everything else, including another chalice and another hammer and a frogspawn, still look great.
Parameters (75g tank + 20L sump)
Ammonia: 0
Nitrite: 0
Nitrate: 5-10
pH: 8.1
Alk: 11.5 dKh
Calc: 500
Mg: 1440
Temp: 79

There have been two changes to the system in the last 2 months; 7 weeks ago I switched from a 6-lamp T5HO to 2x Kessil a360w. About 3 weeks ago, I added a GFO reactor. I was running the Kessils at about 90% after a 2 week ramp-up, but it had been at this level for several weeks before I started to see any bleaching. I have since backed it down to about 65%. I think my params look in line, so is light the culprit?

[MondoBongo]

usually the bleaching that i have experienced in my LPS is light related. maybe try moving them to a shadier spot if possible?

i have my hammer in a fairly dark spot in the tank and it seems happy there.

if that doesn't help, it may be worth trying to take the GFO offline temporarily. most likely this is not the culprit, but since it appears to be the only other change, if decreasing their light doesn't bring them back around (it might take a few weeks) then it's worth a shot.

you might want to take some pictures every few days too so you can track on their coloring. i know sometimes i tend to miss the incremental changes in the tank until i look back at old photos.

love your pibble by the way. very handsome.

[coralsnaked]

lots of time stony corals will eject current zooxanthellae to replace w/ some more suitable to the current light. Takes a couple of weeks to re color up. The mushroom probably wants a dirty little shady place with little flow.

[shesacharmer]

Your alk, calc, and mag are all at the very high end...just wondering if that was intentional...it leaves very little room for error. I try to stick closer to the middle to give myself more margin for error.