I got a group of yellow calvus fry about 3 years ago. As they grew, it looked like I had four boys and two girls, based on size and how they got along. The males were fighting so I sold two. I lost a male and female to illness. The last male and female have been the only ones for a year or so, getting along fine, but never spawning. I recently changed the decor in my tank, and now these two are fighting more, and for the first time, the one I thought was female is getting dark in the face. Does this mean she is a he?