No coral will grow- except this?

[hrdneglcry]

Awhile back I used epsom salt 1 tsp per 5 gallon to try to save a fish. It was just epsom with no additives. According to my refractometer the salinity shot up very high. And it was very difficult to get it to come down. It killed everything. Sinularia, GSP, and palys. It took awhile. Months before it all perished but the Sinualria turned black almost immediately. I recently bought a gsp frag only to have it never open. They old gsp actually died. The purple mat became brittle and crumbled. I have two things on the rock that have not really gotten larger. What are these? They are the only thing growing. I have chaeto in the sump that grows.
I added zeolite to filter to pull stuff out of the water. I run a skimmer and two aquaclear 110's.

 

[I never finish anythi]

Wouldn't the Epson salt have raised your magnesium? Did you test that at all?
I'd list all the tank parameters, so others will have a better idea of what's going on with your tank !

 

[hrdneglcry]

Well over time now some gsp is starting to pop up in tiny pieces. So whatever it was I guess it has been purged.