The only picture that is any use for sexing is the third one down and from that I would say a female .
What you look for is the shape of the top and bottom fins ,on female they are squared off and in males they start to point out .
Can't be 100% from that photo but at 4" you can sex them properly .
Best info on these fish is here http://www.cichlidae.com/article.php?id=76
Check it out.