I am 63 and am in the same boat you are.
I have X20 Tour irons with Project X 5.0 Rifle Flighted, from circa 2008. I had tested the irons a few years back, but opted for the basic X20s instead. I was shifting from Stiff to Regular overall at the time.
Anyway, I hit the Tours OK back in the testing. so I went to Callaway PreOwned in 2010 and got them in PX 5.0 flex, also 115 grams. After a couple of years, the shafts felt harsh on some day. Also, I started getting distance variation, and inconsistent culbhead speed.
Fortunately I had a demo 6i which matched my set, so I had it reshafted a couple of times with lighter shafts. The NS Pro 8950GH R. flex - 97 grams - worked quite well. It went about 12 yards longer than the PX, and noticeably higher. And, it was less work to swing. I really like the feel of the X20 Tour heads, so I'm going with reshaft.
The 8950s fit my swing speed range well, so I ordered the shafts from GolfWorks. I'm going to a local golf shop tomorrow to schedule a reshaft.
I'll send feedback on how they work.
Also, if you've upgraded driver and FWs recently, you also may be getting too much weight difference between irons and woods. If you get lighter shafts, you might get back a more uniform swing tempo.