The advice I'd offer has already been given by others so may be personal experience my help.
For quite a few years I've been noticing right hand index finger weakening. Like, hard to push the button on a spray can. At times worse than others.
After years of that I developed a severe, constant, burning pain on the right side between my spine and shoulder blade. To shorten the story it was a nerve compression issue in my neck. The pain went away after a week and I began physical therapy after that.
The pain was gone but I had zero strength in the index finger and very little in the thumb and middle and ring fingers. I could not pull any double action trigger and a single action trigger was nearly impossible without squeezing the entire hand. And that last part is important in the following.
When I was able to shoot again I had the classic low-and-left hits on target that so many shooters struggle with. What I realized was I was unintentionally squeezing the whole hand to pull the trigger. It is very hard not to do that. In other words the rest of the hand and fingers had to help out the trigger finger.
The point is I think many, maybe older shooters, have a similar issue and don't realize it. We do have loss of strength sometimes and subconsciously learn to compensate.
I got a grip exerciser and a finger exerciser and also made a "wrist roller" out of a long 1" dowel, a cord and a 5 lb. weight. I roll the dowel raising and lowering the weight to work the hand and forearm.
I still have trouble using just the trigger finger without squeezing with the hand. What helps a whole lot is I only very lightly grip with the middle and ring finger and leave the pinky out of the grip equation completely. I grip firmly with the off-hand over the "strong" (see what I did there) hand, with as much of the palm heel of the off hand on the exposed portion of the grip as possible, if that makes any sense to the reader. And concentrate on squeezing only with the trigger finger, straight back.
If I can remember to do all that I can shoot as good as I ever could.
Oh by the way I use the grip exerciser upside down to get more range of motion with the trigger finger, and train the pink and others less.

