Hello, I’ve not posted on here before.
I had two shih tzus and a pug. They all got on really well and were good friends. Sadly one of my shih tzus died last December - she was an old girl. My other shih tzu missed her terribly despite having the other pug - she would be awake at night looking for her friend, barking. So we got a puppy a few weeks later. The puppy is also a pug.
The puppy is now nearly one and gets on well with both of my other dogs. But my shih tzu and the original pug now don’t get on at all anymore. They used to play together etc but now they are very grumpy with each other. The pug usually ignores the shih tzu. They often fight 
but have never actually hurt each other. Today they had a horrible fight, the pug started it, it was because the shih tzu was barking as I put on the leads for a walk.
Obviously the dynamic has changed with the new puppy. I’m not sure what to do. They were going to dog training classes but that has stopped because of COVID. The original pug is a rescue dog, she was used for breeding at a puppy farm. She’s very placid and laid back, a lovely dog. I have had the shih tzu since she was a puppy.
I’m not a very experienced dog owner. I’m not sure what to do.