One colony booming, three others struggling

[TheBeta100]

Hey all! I’m having a strange issue with Zoa’s shrinking and regressing from previously very happy colonies, with three colonies being affected but a fourth growing faster than the other three ever have. I know zoas like a little more nutrients, and I have lowered the bio load of this tank a little bit over the past six months, but I don’t understand how the most recently added colony is doing so good while the established ones aren’t. Nitrates: ~0, I can’t tell with my test but there seems to be some, Phosphates: 0.05 ppm (last I checked was a week ago, but this has been a trend over a few months and phos has been fairly stable), PH: 7.9-8.2 daily range, ALK: 9 DKH (I’ve been dosing small amounts of baking soda to keep this stable), Calcium: 450, Mag: 1400, Salinity: 1.026

Pictures:
Happy colony, with last remaining green colony behind it

Last remaining green colony:

Orange colony (this one Is one of my first corals and never fully recovered from my first tank crash):

One of my favorites, used to be next to the wall and loved it but started regressing and the frag came disconnected from the wall:

Over the course of having these only the flow has really changed, but I don’t think they’re getting too much. Unless they don’t like a lot at night, I have my power heads turn up more at night. Lighting is set for LPS/softies so it’s not too bright, and has been consistent the entire time I’ve had all of these zoas. Any feedback is appreciated!
As a last thing my tank has a lot of limpits, is it possible they’re disturbing them at night?

 

[KC's CNC Creations]

i've had a lot of Zoa look as yours do over the years and it's always been when they were moved into higher lighting, sometimes it can take a few months for them to 'perk' back up, but i've never lost any due to dramatic lighting changes even without acclimating them to the lighting.

 

[Zoa_Fanatic]

I doubt it’s the limpits. I had this same problem and tried everything even moving them down to lower lighting. They just kept dying off for some reason. In the end I got a IV sterlizer. Whatever it was killing them got killed off by it and now all my colonies are taking off. I recommend investing in a cheap UV sterlizer. Whatever was killing mine killed 40% of my colonies ans I haven’t had a single issue since adding Uv.

 

[Tired]

You should probably try to get the nitrates up to at least 5ppm, the lack of them isn't going to help the zoas at all. Make sure you're feeding everything as much as it would like to be fed, and if so, reduce water change frequency and/or size.

 

[chaostactics]

May need more light may need less. Might need to make sure your tank isn't too clean.

 

[blaxsun]

I’m having similar issues with my zoas. Some colonies are doing great and look vibrant while others have just shrunk to a shadow of their former self and only partially emerge or stay closed most of the time. Temperature, salinity and water parameters are all excellent. All my other LPS, SPS and soft corals are thriving - so it’s unlikely that flow or lightning could be an issue.

I’ve basically ruled out everything (including nipping fish) except some sort of tiny pest that might be attacking some of them. It’s very weird and very much hit and miss - you get colonies both thriving and declining in the same locations.

I had been dosing Red Sea ReefEnergy AB+ up until recently (I stopped due to an outbreak of velvet that wiped out a third of the fish population), but post treatment/recovery I’ve resumed that - so I’ll let you know if that helps.