Try playing with the iris and using a blind... but perhaps you need some help with a lens to focus where you should. I don't know how old you are but around 40 your eyes start to change.
Have you played with foresight ring size? Having one too tight can cause issues as well. Around 4 seems to be the way. The more light you have on the target the tighter you can feel you can go, but I don't think it's common to be below 3.8, and 4.2 seems to be a good place to start.
BFTA/NSRA County Coach
CSFTA Chairman/BFTA Rep