I also have a male and female, the male is almost two, the female is one year old. They bark a lot if someone comes to my house but they don't growl. I don't have a lot of company that will ring my doorbell so I try to calm them down when they get wound up. They will also fight and growl with each other when I walk them. Not all of the time but I guess they have their days. I put them in the "Focus" mode when they do this. The trainer I had for Buster taught me this. It gets their attention. I have a treat that they really like and don't get except when we walk. Hold the treat in front of your face, sort of at the top top of your nose, so they are looking at your eyes and say "focus", say it like you would the sit or stay command. They should pick this up rather quickly, Buster was only about 4 or 5 months old when he learned it. I'm still trying to teach Maggie there is more to life than good looks!
She is coming along but not as quickly as Buster did. I don't know if this will work for you but it sure helps me out and keeps them focused on me.