STN/RTN/Bleaching? Should i do anything?

[newfly]

I start noticing the tip on this one acro start turning white. as you can sort of see in the pic, there is still polyps extension in the white part. I have 8-10 other acros in the tank and no sign of stress on the other acros.

The change is pretty gradual. It took a few weeks to get to the current state.

Parameters:

Alk: 8.4
Phos : 0.05
Nitrate: 5
Cal : 500
Mag : 1500

I know Cal and Mag is a little high. it have been this high for months. this is due to All For Reef

Maybe coincident, couple of things happen in the last couple of weeks.

1. My heater malfunction and the temp drop to 66 overnight. I replace the heater in the morning, and gradually get temp get back to 77. This definitely could be the cause of the stress.
2. One of my nero died - replaced it with 2x regular sicce powerhead. 1500gph on random flow, to 2x 660gph on fixed flow. I still have plenty of flow in this 65g tank.
Return - 700gph
2x fixed flow powerhead 2x660gph
2x random powerhead at 70% 2x1500gph
1x (nero) random powerhead at 70% 1x1500gph
3. ICP test show low in a few trace elements. I started dosing trace elements weekly using lower end of the recommendation dose.


Anything i should do or leave it alone? I am thinking not making any changes and hope that specific acro will recover.

 

[Coral reefer]

Looks like new growth to me

 

[newfly]

Looks like new growth to me

Usually, i see less than half an inch white tip from new growth. This is over 1 inch white . If its new growth, that would be a nice growth spurt.

 

[H2OPlayar]

If one coral looks weird and the rest look fine, don't do anything. Check to make sure nothing is stinging the one. As CR said, it looks like new growth to me too.

 

[newfly]

Second acro ( slimer) doing the same thing . The changes on the slimer is quick. I didn’t notice the white tip in the morning.