mine do that sometimes when they out having exercise. Did you have anything on, like washin machine? They dont appear stressed or they'd squeak. I sometimes wonder whether they communicating to each other. My fred and ted do this when they exercise in the hall sometimes. Try them again for short spells to see if it calms. Maybe give them something to hide in like a box or drape a towel from the cupboard like a tent so they have a place to hide!
Firstly what beautiful pigs x)
I too would say they're anxious & the fact your girl is blind makes sense. My blind girl freezes whenever i put her down out of her cage.
I also agree that she is likely un-nerving Buddy too & this is why he joins in although he may not necessarily know why, for me it's a bit like the domino effect, one starts, we all start.