so sorry to learn of the sad loss of your girls.
I know there are visitors to my garden so have always kept mine in a purpose built run. I only have one hen left - an old girl who would probably be picked on (and not cope) if I introduced new stock. Sometimes when cleaning out the coop I leave the door open and she has been known to wander - once half way down the garden before I herded her back. The very next day I was shocked to see a fox standing exactly where the old girl had been the day before ....
Try adding a balcony or two at different levels and perches if you haven't already to your run - it means that some of the hen pecked girls can get out of line of sight of the bullies and enjoy a bit of space of their own, and it also increases the floor area of your existing run without extending it out sideways.