Males will not necessarily fight. I am quite sure the third picture is a male. Not totally positive about your last one because it is a bit small. Especially since you just got them, they will stick together. Males often will get along fine and not fight.
In case you need some references or if they look different in real life, here is a picture of a female. http://www.cichlidae.com/content/ima...es/a031-04.jpg
Look at the nice, round belly.
This is a male. See the flatter, more concave belly and no visible breeding tube?
They are notoriously tough though. Just keep an eye on their behavior and you will know soon enough.