Housemate Problems
The information at the links below relate to problems between dogs who live together. Please note: Even though the exact specifics of the problems written about are probably different than yours, we suggest you read the the information thoroughly anyway, you should find it helpful for your situation.
Dog Fights and Fear
Housemate Fights!
This Q&A focuses on tensions brewing between 2 dogs during meal time, as well as a developing resource guarding problem between the dog and her human; http://woofology.info/troublebrewing.html
What to expect as your adult dog/s and your new puppy learn to live together:
Click http://tinyurl.com/jy3ml5e for an excellent article from Smart Dog University on helping your older dog live happily with a much younger housemate!