Zoa emergency!

[Blyons001]

Hi all! Just a bit baffled and thought I’d turn to the forums. So I’ve had varying colonies of zoanthids in my tank for quite some time now, but recently upon adding a new colony to the tank after proper quarantine, many of my well established zoa colonies are beginning to turn a brownish black color. I initially thought pests so I did a fresh water dip that didn’t seem to help much, nothing appeared to be making a snack out of them. So I turned to lighting as a possible culprit. I dimmed my lighting about 5% across the entirety of the day with no positive results. Any ideas or similar circumstances??

[Blyons001]

Oh and forgot to mention, water parameters are 0 ammonia, 0 nitrite, 5 nitrate. Temp-80.2deg, ph-8.27, salinity 34ppt. Will update with calcium/ alkalinity readings after an updated test.

[FreshSaltH2o]

Any pictures? Any chance of electrical issues

[Blyons001]

This is one of the healthy colonies before adding culprit colony



This is the suspect colony that has been turning brown over time.
I doubt there are electrical issues, I do not have a grounding probe for the tank but it is a possibility that could be causing issues. The lights are never set as they are in the second picture, just had to turn them up briefly to get a good picture of the discoloration.