The tank is too small to breed jack Dempsey cichlids even at this size, I saw in your other post that it is a 29. Anything smaller than about a 75 is going to make it very difficult on the subdominant fish, because they will have nowhere to run to escape their aggressor. I agree with YJ that in your picture, the smaller fish in the front looks like the female. If they are already showing aggression, your best bet would be to divide the fish for now, in my opinion. And when you can get a larger tank, reintroduce them, maybe with some dither fish or even other female jack dempseys if the tank is large enough.