Rbta and a few corals stressed out

[KSean]

my Rbta and a few other corals in the tank are stressed out .
The fungia plate coral, ricordia and the neon green leather are unhappy as hell.
However others are doing fine. (Rock flower nems, acans, zoas , gsp and some others.

Also a mushroom Coral was ripped off the rock and almost split in half but it seems to be recovering. Do they release toxins when stressed?

I tested everything I know of-
ph : 8.2-8.4
Nitrates: <10
Phosphate: <.25
Ammonia and nitrites : 0
Salinity: 1.025

In fact the tank is near perfect in the last 1 year of me struggling to get nitrates and phosphates down. Yet they are unhappy.
nitrate shot up about two weeks ago and that's when they started showing high stress levels. I did a couple of large water change and eventually with the help of nitrate reactor, it came down to under 10 I guess.
I also have GFO, protein skimmer and recently also changed the carbon filter to make sure that it takes away any chemical warfare stuff going on.
Any idea what else to check for ? I'm moving next week and it's only gonna get worse for them
Would at least like to identify what's going on with them!

 

[Retro Reefer]

A single torn mushroom is not going to effect your tank.. what test kits do you use? Any cal, Alk & Mg numbers? Black substrate can potentially be a major issue, some of it leaches heavy metals into your water which can be detrimental to corals.

 

[KSean]

Thanks for your reply. I use API Test kit (the liquid one). I don't have the other test kit. So don't know those numbers unfortunately. How do I know if the sand is leaching heaty metals? It's barely 1 year old. Also I see a huge cyano breakout . It's all over the pump, filter and some rocks.
There's also coating of what looks like a film algae on the glass now and GHA on some of the rocks as well