Ah, was assuming regular crops. Reefs is indeed much more blue.
The dimming may be the hardest of your problems. Looking at the schematics it seems it's basically a boost converter which is current regulated rather than voltage regulated. I really don't know how they react to a PWM switched input (or output). The inductor is where I see a potential problem.
What I'm also wondering - related to plants, but probably the same for your reefs - is how they react to PWM type dimming. After all the lower light as you see is our eyes averaging the level. It's actually very fast switching on and off. Photosynthesis may react differently to this than our eyes do, as the chemical process is started and stopped over and over again.