I have two dogs, Zelda and Jett, who love to play together and tend to get along quite well. However, when I use commands with Zelda, Jett becomes aggressive toward her. She will growl and bark at Zelda, sometimes even attempting to attack her. Consequently, Zelda becomes anxious and does not always respond to even basic commands in Jett's presence. Why might Jett behave this way and what steps can I take to remedy this behavior?