Any time you add a new dog into the pack it is an adjustment. I have four yorkies (3 boys and a girl). They all love each other and miss each other when one is at the doctor or groomer but they do have their moments. The bottom line is that you have to be the pack leader and once they know whose boss things should calm down. I've always had multiple dogs and wouldn't have it any other way. It's a win win situation-More love for mama and they have playmates lol. Just give them both plenty of love and attention and I'm sure things will get better.