If they're only out for 45 minutes and maybe a walk, that is not much exercise for most dogs. Typical dogs will run about for maybe 5 minutes in a yard (or less) before settling down, doing their business and waiting to be let it. Unless most of that 45 minutes really is at a run, there's plenty of improvement that could be made. Part of good exercise involves exercising their minds as well, and the same old yard and the old walks tend to get boring and stop working their minds much. Maybe take them running in a new field (off leash, if you have a safe area and they're trained well enough to come immediately when called).
Is there always/usually someone in the room with them when a fight breaks out? How do you separate them?