Zoas discoloring/turning yellow?

[Kirschy17]

Hey guys,

Ive had this one big zoa colony consisting of 4 different color variants for more than half a year now. Id call my reef pretty succesfull with corals throving from ricordias-acans-acros and montis aswell as an anemone.

Actually i never lost a coral that didnt got eaten by the peppermint shrimp i used to have.

For a week now my red zoas are nor fully open and rurn wierdly yellow in the center. Another wierd thing is i didnt move them for atleast 2 months and theres no new coral nearby. Also i have some of the same type elsewhere in the tank that dont show this brhaviour. My tank is really low on nutrients in general. Also i switched salt 1 month ago trying to slowly rise my ca and kh which have been in the lower ranges.ca(360-400) kh(6-9)

All other corals including softies do very well in the tank. Any idea where this is coming from.

1st pic is the discolored ones(closest to the trumpet in the pic,not as clse at it looks tough), 2nd the ones tha look like they allways did.

 

[DSC reef]

Could just be the polyps morphing. The colony looks great.

 

[Kirschy17]

Sry but what does that mean. In comparison to other coral types im a zoa noob.

 

[DSC reef]

Zoas can change color under different spectrum/intensity

 

[Kirschy17]

I havnt changed my lighting schedule in the 9 months since the tank was setup. Also is there a “rule” if that change is positive/negative? Is there a malnutrition somehow? Too few of certain elements?

So no health issue then overall? Glad to hear