I'm sure you've tried thousands of things... but I found most times when N or P are low, to just make your fish fat. Feed the daylights out of them. I had some problems before with bottomed out nutrients and I started feeding two and sometimes three times a day. I feed LRS frozen most of the time, as it's pretty natural and balanced in nutrients so things dont get sideways. That and a huge fuge soaking up excess nutrients and pumping natural bugs into the display help me keep a tank from going sideways. I also love phyto. It's so good for the tank, it can act as a refugium in limited capacity and doesn't elevate N or P yet is the first stepping stone of the reef food pyramid.
Of course, my tank is sideways now from neglecting it for 2 months... so I may know nothing like Jon Snow.