Go to a smaller target. When I was coaching the Ouachita County Mounted Patrol, I asked a member who failed to qualify what he was trying to hit. His reply was the target. I showed him the X in the 10 ring and asked him to try for that every time. Mentally he tightened his focus and actually tightned his groups.
Work on your mechanics. Consistent grip, sight picture, breathing, muscle tension, body mechanics and call your shots.
Once you have mastered the mechnics, The difference between between 25yds and 50 yds is a mental problem not a mechanical. I have seen action shooters who could hold amazingly small groups at 25 yds and under fall apart on the 50 yd targets. They had a mental problem.