I have the same issues with Wilson and Jack playing rough. Wilson had a 1/2" plus scab on the side of his face a few weeks back from jack. Most the time it's Wilson that instigates the play but it's Jack too. What I've been working on with both of them is purposely making them stop playing when I say but saying "settle." The reason I started doing this from day one is that both are strong dogs by breed and I don't want them to get to the point of rough play that it turns into fighting as they get older. They're getting better at stopping when I say but it's Wilson tha needs to be put on his place by me. The coins in a can really helped and when I used the can I would also say "settle." Lots of times I have to physically make them stop. It's quite fraustrating at times. My best advice is to break them up even when play is good to teach them to settle. It worked really well for my old dogs throughtout the years!!!
I'm sure Tate's feeling a bit displaced in a way too. Having two changes things a lot.