Sounds like your ladies are going through what is known as a season
Sows in season
Girls come into season about every 15-17 days. Often you won't notice, but sometimes, they can be very hormonal. I have observed that this happens more often with adolescent girls, freshly bonded or introduced girls or after an operation that interfered with the estrus cycle.
The girl coming into season can be grumpy or temperamental for a few days (especially if she is the alpha sow). Over the perhaps one and a half day of her season, she will sniff bottoms, rumble, chase and mount her companion as if she were a male. Her companion will either kick her off straight away or allow her to hump until she's fed up, all accompanied by lots of squeaking and often a fair bit of kerfuffle! However, things should stay well below the level where fights would threaten. The humped sow will make it clear when she's fed up.
Well bonded girls will often reaffirm their bond with tender cuddling on the following day.
Coming into season can spark a reopening of the dominance dispute, especially when the undersow is not happy with the way things are. What we think of as sexual behaviour is very often used as a dominance tool to sort out and redefine the relationship.
Our girls sometimes have stronger seasons than others, they do tend to settle within a couple of days at most though
