In my last two trips to the range I've noticed that I shoot a bit low while shooting in the prone position. Anybody else shoot differently in that position.

Also, I was shooting with my compact ACOG mounted on a fixed carry handle. I'm not for sure if I'm doing the same with iron sites (I'll have to check that next time I go to the range).

It's weird, I was shooting the same from the bench, standing, and in sitting position. Just in the prone position did it affect POI. And it was consistant.

What's the best way to correct this?

 

If you zeroed your rifle from the bench on a rest the POI will be different when you shoot from the prone position at the same target (i.e. you got lower, it stayed the same height). As a competition shooter I can tell you that I do use different elevation settings from standing to sitting at the same yard line, but for me it's because my head position is different. Farther back in standing which increases the sight radius.