Sounds to me like Pebble feels the need to assert dominance because Patrick is reaching adulthood. Either Patrick will keep submitting, in which case it will probably calm down over time, or Patrick will decide to challenge for dominance. If he's successful and Pebble accepts it, again, it will calm down over time. You only have a problem if they both decide they're dominant and neither back down, and it doesn't sound like that's your situation
It's just guinea pig business. Nothing is more important to them than settling dominance if it's in doubt. It's a survival thing, at the end of the day, they need to know who's in charge. We can say "there's no need to fight" but we'll never see it from their point of view - they have to hash it out in their own way.