Didn't see it mentioned on the thread - what livestock do you have in the tank? Have you noticed any flatworms or inverts you don't recognize come out (especially at night)? I would suggest looking at the tank an hour or so after lights out.
I know it's unlikely, but have you ever kept a sea cuc or anemone that died in your tank? About 10 years ago I had a tiger tail that died that took down my whole tank (had the cuc for 2 years before that).
Have you ever used copper additives (or any additives for that matter) in the system?
Also, have you done a WC since the original post? If so, what percentage? I notice nitrates are down from 25, so assuming something was done.
Stability of parameters is key, but if you have reasonable suspicion that there is a toxin in the water affecting the corals that resulted from an isolated incident then I would suggest going for the large WC of 30 - 40% and then maybe doing another one again in 2 weeks time if your softies dont perk up. Will your LPS and SPS back track? Absolutely. But it is temporary and they'll eventually readjust after a few weeks.
A while ago I ran into a similar situation, corals were healthy and then one day everything (even my xenia and GSP) was shriveled up for about 2 weeks until I realized the day the tank started to decline my kid accidentally threw a puzzle piece that landed in the tank and only found it about a half hour after it happened. I did a 40%WC and that literally brought everything back to life after a few days. There must have been some sort of chemical in the adhesive on the puzzle piece or something.
Also, I've heard from another reefer that has a tank full of show pieces that after 12 months his tank unexpectedly crashed but eventually got over the hill and has been running a beautiful tank filled with hard to care SPS since. He mentioned hearing the same happen to others.
I will say that with torches/hammers there is a point of no return that once they cross there's no saving them. It could be conditions are improving even though the torches are dying.
Stay strong. We've all been there.