Jds are pretty easy to sex once maturity has started to happen. When they are juveniles, they are impossible to tell apart as all cichlids are.
The best way to tell is by first, examining the fins. Males have longer and more pointed tips or their dorsal and underbelly fins. Second, look at the fishes gill plate, a female will have lots of the color spots while the male has little to none. Also, females tend to be more squat and smaller sized when full adulthood is reached (males roughly 7 to 8 inches while females barely get past 6)
If you can post a pic of your jd, i'm sure we can help with the sexing