Do they have a nest box to lay in? If they don't decide to lay there soon, you may want to put a fake egg in there to encourage them to lay. How many do you have? The red is probably picking on the others because she wants to establish her dominance in the flock, especially if they aren't used to being together. Make sure no one draws blood and it should settle down soon. Good luck!
Yes we have four nesting boxes. Do I need to lock them in the coop at night ? A couple of the reds have slept outside for the past two nights. I am totally new to this so sorry if these are silly questions.