Do be careful with regards to chickens and injuries, as they can be very aggressive towards each other if there are any signs of blood on any bird, I always isolate until healed completely. Unfortunetley, there is always one at the bottom of the pecking order, sadly.
Make sure there is enough space so that they can get out of the way of one another, I have logs, so they can hop up out of the way, when not running around they yard.