Howdy from Texas
Besides the high N and P levels and unknown lighting par levels in areas of your tank we need to consider other factors.
First work on bringing down your N and P levels. Are you making your own saltwater? Is it free of N and P? If so then run GFO or some other phosphate absorption material/media. In your sump you can place more rock or some sort of MarinePure media to encourage more nitrate processing bacteria to grow. Over feeding can be an issue if you have a lot extra food or too many fish. This is esp true if feeding pellets or flake.
Now we have the coral issue. It could be your lights, but what you have are good enough to grow anything if they are placed where they get proper lighting. Your high mag level could be an issue if they are over 1450 with low calcium. It is possible to raise your cal and alk levels by switching to a salt with higher levels. I personally mix both RedSea Coral Pro and the RedSea blue bucket 50/50. I would shoot for 8 to 9 alk. Once you have it where you want, then keeping it stable is the key for those hard to keep corals.
Next we have the battle between your leathers, softies and other corals. They do battle by exuding substances that hinder and can kill other corals. Macro algaes can even do this. If you are not running a carbon reactor you might think about starting one up to filter the substances out of the water.
Hope that some of this is helpful. Hang in there and with help here, you will figure it out.