Blue Gourami sudden color change

Question
I have two seemingly healthy blue gourmais in a 55 gallon tank.  In the tank I have had with them some 3 clown loaches and 5 zebra's (left over from the cycle).  Two weeks ago I added a small red belly peco and 5 barbs.  The fish seem to get along and only chase there common fish mates.

Just this evening I looked at my one of my blue Gourami's and his face has turned extremely dark blue.  Almost as if blood rushed to it, much like a bruise for a human.  I just checked and he was very eager to eat.

I thank you for any input you can give me.  I searched the internet and found nothing.

Answer
Hi Andrew:

I've heard of that when there is a hormone problem or a tumor affecting nerve function. There really isn't anything you can do for either one. It's possible he's feeling like breeding too. Territorialism will cause abrupt color changes. Hard to say.

At Your Service;
Chris Robbins