I thought I'd give the 5 Simple Keys ideas a try. At least the first two (steady head and weight forward) seem simple and important enough that I could start to work on them on my own, especially because there isn't a 5SK instructor within 1000 miles of me.
I guess my normal iron swing I keep my head fairly steady on the backswing, but I lurch my entire body, including head, forward a couple inches in the downswing as part of the weight transfer. So today when I kept my head steady in the downswing it got ugly. So many fat shots, and if they weren't fat, it was poor contact anyway. Seems the bottom of my swing arc is farther back with a steady head. Sound about right? Well how about this: the ball position is already in the middle of my stance with my 7-iron, so if move it back, I'm going to be hitting my 7-iron with 4-iron trajectory.
I'm sure it's hard to diagnose without seeing my actual swing, so I guess I'm hoping some knowledgeable folks will reply with generalities. For example, if the center of the "circle" of the swing arc is behind the ball, how could the bottom of the swing arc possibly be after the ball unless you add some unnatural compensations?