Yep. Half the new piggy user threads is this, exactly. They all do that, to establish dominance. It normally suddenly starts when 1 of them reach adulthood (the other will react to it, etc). The rule I read the most was "no blood, no separate". It's their nature so you want to let them sort themselves out. My first 2 sows were at it every 2 weeks like clockwork. In fact, mine looked a little bit worse than the norm I read about. They were not even territorial, they really wanted to beat each other up. It went on for so long I thought they wouldn't ever stop and it looked like something was really wrong with Ginny for not leaving the smaller one alone. Just 2 sows and it went on for like 4 months. My Ginny gradually became a more caring guinea pig than I have read about anywhere.
Ideally you want bowls and bottles and hidey houses and everything = the number of piggies + 1.
And don't change anything like the location of the furnitures and feeding spots, etc. Unless you put something really wrong. Animals don't do languages or google so they rely on theirknowledge of their home terrain for security and comfort.
Tasty treats MAY calm them down but don't count on it.
Also don't mix this period with any taming, increasing handling or bonding with you type of thing. They are not in the mood for it.
Just let them know you are providing well for them and will leave them alone.