My son had a similar setback at around the 150'mark.
He shut down for a couple of days and did exactly the same 90' 2X 25 for a couple of weeks and built back up to where he could make the longer throws.
He then resumed the schedule and while a little bit behind was fine for the beginning of school and the ortho released him for full activity. The school handled him cautiously in the fall and while he did all workouts was restricted to bullpen work to reacquire mechanics and stamina and was held out of "live scrimm" to prevent him from trying to prove he was back all at once. I believe that was the right call.
He is now doing offseason throwing with no issues and expects to be full ready for the season. We will see how being he responds back to live situations and stamina but I can attest that when he lets one go, the "buzz" is back. its been a long time since I heard that sweet sound and we are cautiously optimistic.