You really need to quarantine the fish before adding them. If you had, you would've known if the now dead fish was sick. Now you could potentially have a major problem that could be deadly to ALL the fish in there.
Yes, females love to join sides and 'gang up'. It is like human siblings... If you have 4, they are likely going to group into pairs. But if you have 3, they are less likely to group up and will be social all-around.
What does your set up look like? They need LOTS of places to hide. Java moss would be a wonderful addition. Be sure you are breaking up line of sight on all levels of the tank. You don't want to leave the top half totally open. Perhaps get a anacharis to line the top?
Seeing pictures of your tank could really help us out on giving you advice to make it successful...
Also, don't keep rearranging decor. This will stress them out and cause more fighting due to needing to establish territories. It is only needed when adding a new female in.