Just like what Mia told them, Rean and Roan didn't go out of the sect. They focused on their cultivation and their side-occupations. When they needed to fight to gain experience, they would challenge those above themselves in the Inner Sect.
Three months after the twins came back, they finally reached the Middle Stage of the Core Formation Realm. They had been in the Initial Stage for over a year and a half, so they were close to the peak of the stage, to begin with.
As one could imagine, Kentucky followed right behind the two since its own cultivation was limited by the twins' cultivation. He was now a Middle Stage Three Demon beast. To compensate for that limitation, Elder Reliance often gave it some other tasks so it could continue to grow stronger.