It is common for one type of fighting to evolve into another. For example, play fighting can turn into dominance fighting and vice versa. Exclusionary fighting will eventually devolve into dominance fighting. Serious exclusionary and dominance fights should be supervised (and sexual fighting situations should be avoided). Unfortunately, the fighting will continue until the conclusion is played out, so you should intervene as little as possible. If you stop a fight, the ferrets will only continue it again tomorrow (and the next day and the next) until a settlement is reached.