I've got two pups that constantly love to play. I think they play too rough. They leave marks on each other. No blood gets drawn but it still worries me just the same. I don't want this playing to escalate one day to pissing one of them off and having it turn into a brawl. I separate them when they play too rough. I exercise them, make them work, and do other random activities with them so it's not like their bored and trying to hurt one another. I just have to get them to be easier. Do you have any advice on how I should do that?