Chlee....you should be a herd leader with EVERY horse. The rules apply to all of them whenever they are with you. All humans should be leaders...it's when they don't that you get in trouble. However, each horse is an individual and may need different handling to establish this.
You shouldn't feel guilty. I have two horses. I love both of them. They both know when I'm with them whether it's one of them or both together, that I am the leader....always. They have their own relationship and pecking order among themselves...but it doesn't matter....when they are with me, all that ends and they look to me.
Once you get the hang of it, the lesson never ends....it's just the way you always handle and act with your horses without even thinking.