zoos depend on light, supplement food is not necesary.
It is possible that your buttons and GSP are growing like wild fire, sometimes there is no real explanation.
For example, in my PC lighted tank, xenias grow like crazy, xenias are supposed to be fast growers, but in many people's tanks that I know, xenias just melt.
Having 9 watts per gallon, will only give light to absolutely any spot. But watts per gallon is an old rule, basicaly it works for plants because any PC light will be enough for almost any plant.
But in reefs what matters is the intensity. I have seen many t5's and metal halide tanks, and they are all packed with coral growth, and they sell frags all the time. Basically the lights pay themselves to some degree.