Lps seem to losing color

My sps seem to be doing well but all my other corals lps mostly seem to be loosing color especially the purple orange red pink and yellow colors, I am currently running a 6 lamp t5ho ati sunpower on a 72 gallon bow front (tanks about 18-20 inches depth) fixture sits 3 inches above water level. All water parameters are checked regularly and all are optimal. Bulbs are all fairly new and as follows from front to back...

Ati blue plus
Ati blue plus
Ati blue plus
Hagen life glo 6500k
Ati blue plus
Ati aqua blue special

SpS more toward back is this reason for aquablue being placed in the last slot

Could it also be that I have been using kalkwasser in my auto top off?? I defenitly realized ever since I started using the kalk instead of TLF two part my coralline algae on my rocks has died out a bunch but maybe this could be because of the lighting and not the kalk, I had better pink and purple coralline growth when I had a 4 bulb fixture that was giving off minimal light due to bad reflectors.... PLEASE VOICE YOUR OPINIONS ALL COMMENTS AND SUGGESTION WILL B GREATLY APPRECIATED!! Thank you

 

some time back i had a big Mg spike. I noticed that dulled my colors. Got it back down to ~1350-1400 and color seemed better.

I also notice it when my bulbs get old.

 

Certain LPS do not keep their original colors under t5's. (I'm running 4x24w t5ho's. 1x aquablue special 12k~2x blue+ and 1x purple+) I once had an Rainbow Acan Enchinata. Most beautiful coral I've ever seen and had to have it. It had purple/blue/yellow/orange/green and red! Wasn't in my tank a month and it lost all rainbow coloring. Dealer informed me that it had been kept under MH for quit some time. Now I've got this less then pretty, slightly orange/brown healthy growing no longer rainbow looking acan enchinata It's just the nature of the beast.
I don't think it's your parameters. If it were your sps would definitely be showing it. Keep in mind when buying corals that most sellers are keeping them under MH or LED's and will not look nor maintain their original colors, period. I've yet to see otherwise. Especially those with many different colored pigments.

 

Some corals take a long time to adjust to different spectrum IME. How old are the bulbs? If new, then that could be why. If old, then I would probably agree with Peredhil that the bulbs could be getting old, or that there is an excess of some metal Not just magnesium, though, other metals can interact with fluorescent proteins and deactivate them - also, too little of certain metals could cause dim colors, but in our systems, I tend to doubt trace metals get too low for various reasons they do accumulate over time though. If that is the case, perhaps a poly-filter or cuprisorb or GFO would help, as they can all bind various metals.

IMHO lighting is much more likely however, as is lack of food.

 

Thanks for all the feedback and it's funny u mention that about the rainbow acan because I too bought a 150 dollar beautiful rainbow acan wit orange blue green n purple in it... Now it's just a dull orange, it happened after about a month n it's lost color ever since...I'd give anything to get my coral back to how it was, at the end of the day we r trying to replicate nature in our home n no matter how good u are the corals will never look as good in ur tank as in the wild

 

Acans don't do well under strong lighting. I always keep them shaded.