Anyone up late tonight? Question!

Is it common for a Mandarin Dragonet to lose color at night?
Just before my lights went out he was bright and vibrant and swimming/eating with no obvious problems. I decided to peek in the tank tonight and happened to catch him "sleeping" down among some rock. He looks very washed out. Almost like the brown spots are still OK, but all the blue is gray. Has anyone seen this before?
Salinity 1.023
Nitrite 0
Ammonia 0
Nitrates about 20 PPM
phosphate 0
Calcium 460
PH 8.2
Pods are everywhere in the tank 200 lbs live rock, cured for 9 months in the tank. Phyto is fed every 2 days.
Any ideas or do I worry 'till morning?

 

He's back in action today!
Thanks for the replies!
That was weird. Even his eyes went white. I read alot last night but couldn't find anything on it. Maybe it is a defense, although I thought in the wild Mandarins were nocturnal.
Well this is at least a good lesson in how hard these fish are to take care of. I spent 9 months getting ready for this fish and still spent a sleepless night because I didn't understand it.