Some DS help with dog fights in the home?

It sounds like Dominance fighting. The Cairn is trying to show the other dogs who is boss. This usually happens from 18 months to 36 months, plus whenever a new dog is brought into the home. They just have to fight it out for themselves, until they establish priority. It can get bloody, as I had that happen a few years ago with two Shep. mixes, as both dogs were dominant types.