The 1st thing I see when teaching with video, most golfers play the ball to far up in their stance especially Irons. They have a tough time trying to find the Bottom of there Arc. The other cause I see is that Golfers Chicken Wing (or there lead Elbow Bows away from body). To find the Bottom of your Arc start with hitting balls with Feet close together then separate them little by little. Second answer would be swing a WEGDE in your lead hand and make some swings with No golf ball. Should notice that your Arm folds.