the ones with the larger heads are going to be males as you can see the yellow dots on the fins in the new pic you just posted. the ones with the smaller heads are your females no dots. jsut like a RTM only with out the red. but i have no idea if the head shape is normal or not. compared to RTM the males look alot alike but your females are throwing me off.
as i was putting in the tank i looked at their vents but they all looked the same so i figured it was still too soon to tell but there are a few that are obvious males. so you're saying that they're the yellow version and not rtms, right? my bad photo taking aside they're a real nice orangey/cooper color.
after looking around a little bit is it possible that they could be parachromis sp la ceiba "yellow head"? i say this because the male in this picture from one of mojo's posts
i'm wicked lost on all of this, i'm leaning towards loisellei but i can't find anything about the weird head shape..
<edit>the yellow head loisellei variant but idk</edit>