Alright, Allsps40 I'm going to jump on board because I have no clue why my color has faded. I know we both keep 40breeders so maybe it's the 40br curse? Were pretty much running a similar system so maybe we can figure something out. I have ton's of sps as you do and several frags have lightened in color dramatically and another acro has semi browned and a purple stylo has lost a lot of color as well. I will take pics when I have my camera handy and post them but for now i'll post numbers. I picked up several frags from Kataro (sorry folks allsps40 and I are local to each other, so if it doesn't make sense I apologize)a couple months back, a grape juice acro, purple monti cap and a red planet. All 3 looked absolutely stunning in his tank, fast forward several months later and all 3 have a complete lack of color. Now they aren't bleached by any means but just seem to have faded dramatically.
Cal-450
Mg-1500
Alk-9
ph-8.3
Sg 1.026
Top off is with kalk water and I dose Vit c. (it was the same scenario without the vit c as well, so I know this isn't the cause) all other system specs are in my sig.
I use RSCP salt and noticed a slight color change in the right direction but still not coming full circle, actually not even a quarter circle. All other frags are doing fine, but who knows if they are even showing their full potential (which I highly doubt). LPS and zoa's are doing great.