Scrambled Eggs Zoo Skirts Turning Brown

[RYcube2951]

I have a large colony of scrambled eggs zoos. The skirts on many have turned brown. The ones on the left side in the photo still have their natural colored green skirts. Growth has never been an issue with them and they have always been in the same location of my tank. Here are some tank specs:

Tank Type: Coralife Biocube 29G
Lighting: Current USA - 1 actinic blue led strip and 1 daylight/actinic combo strip
Flow: main pump plus Hygger powerhead
Filtration: Tunze 9001 Protein Skimmer; in-tank media basket with polyfloss pad and Chaeto macroalgae
salinity: 1.024 - 1.025
Temp: 78 degrees
Phosphates: 0.3
Nitrates: 15 - 20
Alkalinity: 9.0
PH: 8.0

maintenance: weekly 10 -15 percent water change. Not feeding the corals.

Any ideas/suggestions on the brown skirts and how I might address the problem is much appreciated.

 

[T-J]

Not sure if it's what's causing the issue, but your PO4 seems incredibly high.
Also, it's not uncommon for corals to shift colors based on lighting and tank conditions.

 

[AlgaeBarn]

Not sure if it's what's causing the issue, but your PO4 seems incredibly high.
Also, it's not uncommon for corals to shift colors based on lighting and tank conditions.

Also possible due to other corals around them

 

[Danmuges]

Did you work out the problem? Mine keep losing the skirt when they are in my frag tank but in my display and nano they come back

 

[RYcube2951]

I think the way they appear to me might just be the way my lights shine on them. The brownish looking ones could actually be green. The only way I could probably be sure is to remove the rock to get a closer look but I am not about to mess up my aquascape.