Shih Tzu Q&A
How old are the puppies? Have they been neutured? If not, speak with your vet about when they can be. This will help some. Training will also help, setting you as the alpha in the house and allowing them to socialize and burn off some energy. The natural order is a male and a female to avoid this problem.
pack structure. You need to establish it. You are the pack leader. You need to establish who is the top dog and let them know it. The top dog gets fed first. Always. Don't let it be an issue. Dogs are pack animals and are happier that way.