Help needed, dull/brown SPS

[serbusfish]

My tank has been set up for around a year. Up until late February everything had been going great, I had a nice selection of corals, they had good growth and good colour. But something has happened since and I have no idea what has caused it. Some of my corals have very dull colour, 2 monti plates are basically grey, and a couple of acro frags are brown. My Birdsnest which grew from a 1 inch frag to a 4 inch across colony is slowly bleaching from the bottom, as is a Stylo. Another issue with the Stylo is some of its polys arent coming out fully.

The problems started when my skimmer broke down, my nitrates rose to 25 and a few acro frags went brown and my monti plates looked a little duller. After 6 days my skimmer was working again and after many water changes my nitrates were back down to 10. My colours started coming back, but I still needed to get the nitrate lower so I then started dosing Red Sea NoPoX, ive been dosing for 3 weeks but im only using 2.5ml, my nitrates are staying at 5. I was running GFO but I removed it since I was using NoPoX. I use a small amount of carbon in a filter bag as I have a couple of soft corals. Lighting wise I have a Maxspect Razor 320w LED unit, photoperiod is 6 hours full intensity with an hour of ramp up time at each end so 8 hours in total.

I tested my water 30 minuted ago and these are the results:

SG 1.025
KH 9dkh
Mag 1350
Cal 420
PH 8.0
Phos 0.03
Nitrate 5

These are the parameters I have been keeping the tank at for ages so I dont understand what is causing the problems, and im started to get desperate for a solution. The issues are only affecting my SPS, but not all my SPS. I have some acros which are growing, I have Monti Digis that are colourful and growing, and I have a new pink birdsnest frag which is very colourful.

Any help would be really appreciated, these problems are genuinely making me consider ditching SPS and sticking with LPS and softies :mad2:

 

[djbon]

IME, potassium play an important role. Check your potassium level.

 

[serbusfish]

IME, potassium play an important role. Check your potassium level.

Potassium is fine, its currently measuring at 440.

 

[serbusfish]

bump

 

[djbon]

I'm not a WC guy, but maybe your tank is lack of trace elements and other ionic issue. Light spectrum could be another area you need to look at.

 

[serbusfish]

I'm not a WC guy, but maybe your tank is lack of trace elements and other ionic issue. Light spectrum could be another area you need to look at.

The Maxspect Razor's colour spectrum covers a very wide range, the blue channel LEDs cover the entire spectrum from 400 - 480nm, and the white channel covers 3000 - 3500k, 4500 - 5000k, and 6500 - 7000k. The white channel also has additional 455 - 460nm + 465 - 475nm LED's.

I do 12% water changes once a week, that equates to nearly 50% a month, surely this is plenty to keep trace elements in check?

 

[Sapelo]

Well I dont know if this help and I know it's not what you want in a response (a smoking gun or "fix" is what we all seek when things start to go wrong) but it may simply be a matter of giving things more time to recover. We know that montis and birdsnests are some of the more forgiving sps so they may simply have handled the deterioration in water qualify better than some more demanding sps.
I know trace elements are important but personally I rely on my water changes to manage most of those things rather than trying to dose another item. It does not sound like you were dosing other trace elements before so I dont know that I would assume that is a problem now. Testing would confirm that of course.
I think if I were in your shoes, I'd go back to what was working prior to the skimmer breakdown and try to keep everything as consistent as humanely possible.
Sps in general hate change and you had a number of changes. Now you have to get back to your sweet spot.
Just my two cents...