I would tend to try pair breeding before colony breeding to be honest Candace. Of course it is up to you but here is one suggested plan... :P
If you are serious about breeding then get two males (preferably older than the females) and introduce them using which ever method you prefer - split cage etc. into two seperate enclosures, and see how it goes from there. Others may suggest different, this is just what my experiences have taught me. Younger males can hopefully be used if you get them quite soon.
Of course this would mean you have two breeding pairs so maybe you are best to get another female (from the original litter if possible) and a new older, unrelated male, and thereby have a pair of same sex hamsters and your breeding pair...
And then at the end of the day you may end up with a huge fight on your hands and need seperate enclosures for one, or worst case, all of them...
I was a little worried to hear of the goings on with your little girls. Keep a close eye on their back-ends as this is where damage seems to first show up when they fall out. Removing them from their small petshop enclosure, and the supressing presence of their other litter mates, and giving them such a lovely big tank will unfortunately also mean their little personalities get a chance to develop, and like all true siblings they don't always get on when this happens... Try giving them two of everything - two houses, wheels, food bowls, water bottles etc. and see how they go.