You added a new snake. It's like when you add any other animal be it horse, rat, dog, whatever. The herd hierarchy has to be established. Honestly I think you should separate all three snakes. Keeping ball pythons together is never recommended. They are solitary creatures that only get together to breed. That encircling behavior is him trying to dominate the other one. I've got eight snakes and they all have their own tubs or enclosures. If it's a big tank you can put dividers in it to keep them separate. Tubs are also a cheaper and spacing saving option than three tanks.