Pair of blue throat triggers - male losing color

[Olathereefer]

I purchased a male and female pair of blue throat triggers for my reef tank. When I purchased the pair the male had bright yellow on its fins and bright blue throat. Now, three months later the male has lost all of its yellow and the blue throat isn't as bright. He almost looks like the female. I have tried a variety of food including mysis, brine and flake foods. They also like to eat the algae sheets intended for the tangs. Any thoughts on how to bring his bright colors back?

 

[Dmorty217]

What is the size difference between the two?

 

[Olathereefer]

They are the same size. I thought the female could turn male but it seems like my male is turning female.

 

[Dmorty217]

Do you see any aggression between the two?

 

[humaguy]

happens all the time with these fish, even when everything in the tank is perfect

 

[Olathereefer]

They get along and are not aggressive towards each other.

 

[McPuff]

I had a blue throat and the same thing happened. It was healthy and there were no other triggers in the tank. I kept it well fed but it just kept losing color. Probably is due to lack of aggression that would bring out more showy display.