I've never seen her do this before but, 3/4 of her has turned totally white. I know fear will do this to fish, but will a WC do this also? Her behavior is fine and she's eating.
I had a Yellow Watchman Goby that turned gray and never colored up again. Very happy fish, just lost its color and never got it back? Reeferrob has had it in his grow out tank for almost a year with no changes in color?
my yellow watchman changes color while sleeping or hiding if it feels threatened, its like a camouflage or something they do, maybe yours is doing the same, its back to color within 3-4 hours.
I have a Tailspot also, they have stripes when they sleep. They'll turn white out of fear also. I had mine do this once when I was transferring him to a different tank. The Ecsenius genus is known as being color changers.