Your flock of 5 were fine with the set up because they all knew each other already, like siblings moving into a new apartment together. But now... think of integration as being more like new roommates moving into that shared house/room - there's bound to be some difficulties as they learn to co-exist.
The link that 3KillerBs provided has good directions on how to convert this into a bigger coop space, or you can take Ridgerunner's advice and see about letting the newcomers sleep in the run for the time being, if that's safe enough.
