There are a lot of different reasons for this so I can't say for sure without seeing your brackets, but some common problems:
1. You're too far onto your toe pick and/or not using your knees enough, try pushing the edge into the ice more on the exit
2. not enough speed into the turn therefore not enough out
3. breaking at the waist after the turn can lead to lack of knee bend and too much toe pick
4. the turn isn't clean ie. it's scraped, this is most likely due to a lack of pressure on the entry and exit edges and lack of knee action through the turn
5. the upper body is working against you through the turn, ie. you're not checking the turn properly therefore leading to other problems that lead to the turn stopping dead
Those are some of the common problems, but I really need more info to give a more concrete answer.