Sure, it is easy to look at a situation like this and say there are "issues in the room", "Pettersson's performance is affecting teammates", or "J.T. Miller is toxic", but in reality, we can almost guarantee it has nothing to do with issues off the ice. Hockey is a physical and competitive sport, and in battling drills, you want guys simulating the game and competing hard, and with that, emotions get elevated.
All in all, there is probably nothing more going on here then some fiery competition and it would be ignorant to paint it any differently. If anything, it shows EP40 has some fight and care to his game right now, in which fans should be happy about.