There are pictures of males calling then fighting in Jewels of the Rainforest book. So I would say that males can definatly fight. Especially around food. I've seen some light bullying in my cobalt tincs, but it isn't too bad and everyone gets the food they need. So as long as your's are eating well, I wouldn't worry about it. I wouldn't say you have females just because they fight.
-Ben
-Ben