I hope they are Maingano's - a little less aggressive than Johanni especially given your relatively smaller tank size. And absolutely wonderful fish.
Johanni females are yellow/orange so if they are that species, then yes you have all males. On the other hand Maingano males and females are both blue, with the males just darker in colour. If you have Maingano's, especially if they are young, you may have a mixture in your group of 3.
Phew thats a lot. But I got heaps of help from here when I started so wanting to "pass it on" as much as I can.