I have been running all LED in my nano 29g too.
My setup is 2 strings of 12 Cree Q5.
Originally I had 12 cool whites and 12 royal blues. Had some issues with coloration and bleaching as many of you have experienced too.
I had bleaching on some acros right from the start. Some LPS that were too up high, were receding and after moved down, they got much better.
According to my observations, the bleaching and receding was from shock and not intensity. This is just what I have observed and nowhere near something that is concrete or something that you must do to your tank either, I have to add.
I originally thought it was too much light. I then decreased intensity since I have a dimming driver. Everything seemed to loose color and brown out.
I ran a pretty brown tank for a while until I was so depressed that I decided to start playing with different factors, including wavelength, intensity and exposure time.
I replaced 2 cool whites and 2 royal blues for 1 red, 1 green, 1 warm white and 1 UV.
After the change I have also found out that red bugs were messing with acros. So I started treatment.
I then increased intensity and exposure time, but I inverted the intensity that I had originally set. I had originally set more white than blue. I now run my blue string at 90% and white at 60%.
I started to see much better results.
I can say for sure and from experience that the color spectrun does affect the coloration.
I have a moni I got from JAR that I decided to do a little experiment.
It was totally brown and it still is. It was supposed to be fluorescent green.
Since I had placed all these new LEDs bunched up in the front of the tank, I broke a little frag from the monti and placed close to the new LEDs, while the original was towards the back.
Well, the little piece got its coloration back and the original is still brown.
Richard came by last weekend and saw it with his own eyes. That was when he decided to get his UV LEDs too.
So, according to my observations, I think mixing a lower wavelength then the royal blue is needed to get better excitation on the fluorescence of some corals.
I'm yet to do the same experiment on a superman monti that I have towards the back too. Its polyps are green, instead of red.
Doing fine, growing and happy, but with different color than when I got it. They started red, then after a while to orange and now to green.
That's my experience so far with LEDs.