Nearly all my coral died overnight...HELP!

[Phludd]

Well just a quick update from last night:

I got home and at that time the low output LED strips had been running for 2hrs.
Everything looked horrible, worse that it did Tuesday night. So I raised the MH fixture about 4 inches and put my old bulb back in to see if anything would cheer up.
After waiting about 2hrs with no noticeable improvement I decided on doing a large water change. I made this decision because even with the bulb being the likely cause of all this there has definitely been some die off all around and that in turn had most likely had an impact on water quality. So I performed a 40% water change.
I feel I have done all I can at this point...I will just have to wait and see what pulls through.
Right now the LPS do still show signs of life, even though they have very little PE.
The acros have about 80% tissue loss on average. The other SPS are definitely damaged but have shown SOME PE.
Of course the cheapest and least important coral I have ..Mushrooms, Ricordea, xenia, and GSP all seem to be doing fine.
Both fish, all 3 snails and my hermit are all fine as well.

I will update the thread later with how things turn out.

I appreciate everyone’s input and advice.

 

[Phludd]

Another update:

Got home on Friday and the large green a.tenuis colony had lost half its tissue, is was sloughing off in big flaps. So I tossed it
Since nothing had gotten better or had minimal improvement I was still suspecting I had a water quality issue. Everything I could test for was well within acceptable ranges.
So Saturday I went and bought a 'canary for the coal mine', a small green stylo frag. To see how it would do in my tank.
I acclimated it and went to place it, when I noticed both my other acros were going through massive tissue loss, it was blowing like sails in the wind. So I tossed both of them.
After acclimating the sylto and adding to my tank it had no PE for hours, which made me very concerned about my water quality. Then right before lights out it showed a small amount of PE.
Apparently it just need some time to settle in because yesterday it had full PE and looked better than it had at the LFS.
Also my elegance and bubble started to really come back to life yesterday, showing about 40% of their original size.
I dont know it their sudden improvement was the fact that I removed those dying acros the day before or just coincidence..either way it was good to see them on the rebound.

Looks like even if most of my coral recover it will be a long process, but its good know that my there isnt some underlying issue with my tank water. I am convinced now that it was indeed the lack of acclimation on the G'mann 17.5k bulb that caused the meltdown.
Expensive lesson learned.