One factor you may be overlooking is your irons are about 8 years old and depending on how often you play the grooves might be worn down and affecting spin/distance. Even 3-4 yards due to grooves may not seem like much, but pair it with an aging swing and potentially a too heavy of a shaft and now it's a 6-8 yard drop. Re-shafting is a potentially expensive endeavor, might be worth looking into the newer line T100 or T200's and try with lighter steel or even a range of graphite until you find something that makes sense to upgrade to.

Although I am a bit older than you and always played the DG S 300, those issues were front and center for me for some time until I made the switch to graphite. I have for a long time believed that the shaft is everything and with so many choices out there now, you can find the right one for you if you go through the fitting process.

Dial in your swing with a fitting where you can try variety of shafts. You'll then have the data to know the correct flex, weight, launch and feel from the shaft you want.

I went from an 85g R flex steel shaft to a 130g X flex steel shaft after a fitting..

If you go for a fitting, the fitter can compare how you hit, let's say your current 7-iron with other 7-irons/shafts. That would be the only way to really see if you need a shaft upgrade. Bear in mind that getting your irons/wedges reshafted can get pricey so a new set might be better in the long run.

Good luck!

You should go for a formal fitting, that's the only way to tell for sure. We all loose a little off the fastball as we get older. When I turned 50, I went from a KBS Tour S 120g to a KBS C-Taper Lite R 105g. Huge difference in ball flight and consistency. And as others have said, if your AP2 912 have a lot of rounds on them, you will greatly benefit from fresh grooves.