Again before you do anything, let this media dry up, I mean dry, like 2-3 “ from top .
Then flush, with ph water around 6.5-6.8.
Flush till you get run off, then let dry
Flush again, each time noting what the run off ph is
Let dry in between, I’d suggest you remove said plant if possible to the outside , and do this there, as I suspect the fungal issues are vast, kelp feeding does this same thing to me, and I’ve stopped using kelp grow feed. I actually just use fish emulsion with some amendments.
But the goal is to get this thing dry and flushed, and flushing only removes salts. Your organic matter will stay intact.
Once this is in control then I’d consider changing the pot and adding more new soil. And rebuilding the macro/ micro herd.