@crazybasenjimom When you say they get lots of exercise, is that structured walks or running around in the back yard? Structured walks where you are in command and the leader, are good exercise. Running around in a yard is exercise, but it does not reinforce the structure of the pack or establish you as the strong leader.
Leaving them to it in the back yard, they are likely to sort their own problems out just as they would in the wild. Nature is brutal and no doubt there will be dogs who dominate and dogs who suffer injury.
Without more understanding and information, it’s hard to say what would help. If she is dominant, taking her inside and establishing yourself as the dominant force might work. However it might also lead to you being bitten instead.
On the other hand if she is fearful, one of the other dogs is dominant and it’s them that need the leadership. Without you as the dominant leader, they will operate as a pack and enforce their own laws.
I agree with Debra, a food first step is a full blood and thyroid for all the dogs.