Recently I noticed my elbow was getting high, and that my ringfinger was getting very sore (the tip was bruising).
I realized I started gripping the string with just the tip of the ringfinger, while the 2 other fingers had a deep grip.
Once I realized that, I made a conscious effort to have a deep hook with all three fingers, and feel the pressure of the string mostly on the middle finger. My elbow came back down and my groups retightened. Make sure you do have a deep grip with all three.
Marco