Zoanthid colony closing up

[dwolson]

I have had this rock frag with zoas for a little over month now. They were open and multiplying ever since a couple days ago. Half are closed up, especially the smaller ones. The only changes I did that I can think of was to replace my carbon with some new carbon. Also, I did notice an Alk swing from 7 to 9.5 following a 10% water change at the same time as the carbon change. What gives?

All tests done with Red Sea kits:
NH1/NH4 = 0
NO2 = 0
NO3 = 1
pH = 8.2
Sal = 1.022
Calc = 475
Alk = 9.5
Mag = 1300
Temp = 79F

Lighting is 5X T5 from ATI (3months old), on 8hours per day.
Tank is a Red Sea Max 250 (several years old now).
Water comes from 0TDS RO/DI
Have been using Reef Crystals salt

Thanks for the help!
Dave

 

[dwolson]

Bump

 

[dwolson]

I should point out that all my other corals are in good shape. Sps lps mix.

Ideas?

 

[dwolson]

One last bump

Dave