Everyone is thinking about love on this Valentine's Day. All animals have bouts between themselves of disagreements. That can be normal or may turn sour to needing intervention.
Dogs may have upheaval such as, you took my treat, you are in my chair, you stepped on my tail, on and on it goes. There is a quick outward display of disagreement, possibly a growl or a snap to settle the situation. Most of the time all is forgiven and it's back to getting along. In general, dogs that live in the same household want to have a peaceful day.
When the disagreement isn't being resolved, growling and snapping persists to a serious level, then the humans need to step in to find an acceptable solution. It may be moving the sleep areas further apart, separating them when food or treats are presented. It may help to give each one time alone going for an exercise walk. Sniff walks each one alone with their human can also clear the brain of worries.
Seeking a trainer that can visit may be needed to view the conflict issues. An outsider's fresh perspective may see things we can't see being in the family with them.