What food are you feeding?
Has anything changed in your life? Schedules. Illness. Arguing. New bones or toys.
The puppy could very well be a part of the trigger to this problem. These same aged, same sex, dogs could be bickering for their position in the pack now that the pack is growing and involves the education of a youngster.
Often as a pack grows the weak links in the pack start to show up. The more children in a classroom the more structure the teacher needs to maintain harmony.
Love Them & Lead Them,
~Elizabeth & Doug
Dog Training the Way Nature Intended