I don't know that chemistry is the issue here. Yeah, it's a bit off, but no single one of those could have killed this coral. Even ammonia would kill your clownfish before a coral cared. Immediately doing a 100% water change with perfect water would only stress this coral further at this point. Pouring chemicals in to "fix" your parameters will probably kill not only this coral immediately, but most of your other ones over the next couple days.
It's probably not getting enough light and flow (the polyps higher up are retracted, that's what the black dots are on poci).
The time to save this would have been 7 weeks ago when the polyps weren't extending correctly, although at the end of the day, your tank may simply be too new for SPS corals.
At this point, there is almost nothing you can do for this coral. Check to make sure its light and flow are good, move it away from the algae, and perhaps frag a bit off the tips. By the time it's peeling at the base like this, it's a goner though...
Time to focus on the other corals in your tank and make sure they are doing well.