Yellow is a light thing. Daylight spectrum will really help. So will lots of intensity. I only have the SB Yellow Tort, Wolverine, Pikachu and OG Tyree Pink Lemonade, but they are more yellow at 400+ PAR and under whiter spectrum. In the frag tank under 10K, they are even more yellow.
If you are a T5 guy, then see if you can work a GE 6500K in there. If LED, then whiten them up a bit.
The brightest and intense yellow color comes with lower (near NSW) parameters, so you are good there on N and P. More would make them darker and yield more towards green - richer, if you will, and not brighter.
There is no tank that can color all corals great. I keep my tank with just a trace of N and P because I like the growth and also like the bright colors with greater contrast, but my red plant, for example, is not as rich and dark of a red as others. There are tradeoffs, but very high light and NWSish parameters is where I like it.
Do you have the Hannah Ultra Low? It gets pretty low.