There are 2 types of low nutrient systems.
1). Those that are there naturally.
2). Those that use GFO, Organic Carbon or Lanthanum Chloride to get there.
#1 is fine and you don't need to do anything. For #2, you need to make sure that you are sending a LOT of nutrients though before they are exported artificially - this is not a great idea except for the ultra-experienced that are looking to tweak a specific thing. #2 tanks are always walking a thin line of ultimate color/growth and crashing.
My tank is #1 with N of .1 and P of .005 to .01 and I just feed my fish 3x a day with pellets and then most nights with mysis. I do not feed the corals or dose any aminos or anything.