When do Fish get their Streamers?

[Aspect]

Hello, I have an Orange Shoulder Tang and Blonde Naso Tang that are growing quite fast. Both are 6" or close to it. I am wondering when their streamers should start coming in if they are male.

 

[MERKEY]

I think around 1.5 years for most.

Diet and size probably add to this so no 1 tang will grow exactly the same