You can ask at the
main thread - looks like there are more people all the time.
I tried (for feathery bryopsis) ESV liquid Mg additive, Seachem Reef Advantage Mg, Kent TechM - up to 3 weeks after reaching 1600ppm, total 1.5 months, nothing worked. Had one more treatment before - August-September, with Seachem.
TechM was least liked by tank inhabitants - anemone and green and cocoa porites. This is sps, clams, anemone tank with intense feeding. Others are doing well and grow.
No ammonia. Schedule of raising Mg - in the main thread, I did it slower.
HTH.