Please help with SPS! Birdnest, Monti deteriorating!

[cwinn]

Hi, I have a 180g tank and started adding SPS about 2-3 months ago. Started with some birdsnest and monti caps which did really well for a month or two. Coloration was great and they were growing. For the last month they have gotten worse. Didn't make any drastic changes so unsure as to what the cause may be. (birdsnest in last week). Pictures below of before/after. Any help/input would be greatly appreciated. Not sure what is going on, all that is showing up "test kit" wise is high nitrates. All my zoas, ricordeas, LPS, fish are thriving

Tank info:
SG: 1.024
Alk: 9 DKH
Calcium: ~420-460
Mag: 1450
pH: 8.0-8.2
phosphates: non detected with test kit, no nuisance algae
nitrates: 20-50?, have API test kit so can't get an exact number

Mag18 return pump
2 MP40 run pretty low
Huge SWC 300 Skimmer (came with tank)
Fuge w/ chaeto
GFO reactor
ATO w/ kalk
Lighting: DIY dimmable 3w Cree setup. 1:1 RB:CW with some red, green, purple LED mixed in. 75 RB, CW combined. 12 red, 12 green, 12 purple.

25g water changes every 2 weeks, sometimes 3. Only RO/DI water. Instant Ocean salt

The ORA green birdsnest is showing skeleton and the monti has lost its deep red color and now fading to white with some brownish growth on top. I have about 5 frags of the monti scattered throughout the tank and they all have suffered the same. I have tried moving the birdsnest to low, medium, high placement. I have a blue birdsnest that is started to show the same deterioration in skeleton (noticed change in this one yesterday)

I was 2 part dosing, timer failed and overdosed some alk. Alk rose to 10-11. Stopped dosing and week later it was back to normal of 8-9 DKH.

Ideas??
1. High nitrates?
2. Inadequate lighting? Too much? Too little?
3. Flow?

 

[M007]

The ALK spike likely set them off, N03 at 20 to 50 isn't helping. Both pics look pretty bad, sorry for your loss.

 

[cwinn]

The ALK spike likely set them off, N03 at 20 to 50 isn't helping. Both pics look pretty bad, sorry for your loss.

thanks for the quick response. even though the alk has stabilized is there anything i can do at this point?

 

[M007]

The difficult part about ALK burned SPS is keeping algae from colonizing the bare skeleton and taking over. You say you have no nuisance algae so you may be able to save them with reduced light and patience. If they keep peeling tho I doubt the is much you can do. It happens, caulk it up to "lessons learned".