Large sps colony dying from the bottom?

[Animal-Chin]

Ya I agree and I do still have a reading of 5 so there is some in there. I thought at first maybe the reduction was the issue but I reduced the nitrates over 2 months so it wasn't a sudden shock to the system. I have way more sensitive sps coral in the tank that show no sign of stress either, its just this one big coral.

Gonna dip it tonight I guess. I'm also going to buy another alk test kit just in case mine isn't reading correctly.