Now I realized that this is an old comment, but I hope it still is in effect the item for you.
The mine have the same difference in their foreheads. Attached is a photo.
In theory, your fish would be the No. 1 male.
Pay attention to the shape of the operculum. In males appears to be squarer and more rounded in females.
On the internet we read that the females have red eyes more during the rut. Also that black spot on the side is larger in males.
Greetings from Costa Rica