If you go back and look at video of some of his good starts in 2021, 2020, he doesn't really pitch up in the zone for whiffs.
Mostly you see slurves below the zone for strikeouts. Or fastballs for called or swinging strikes but kind of all over the place - inside, outside, sometimes missing his spots by a foot.
It just seems like his pitches have lost some "shape" or some type of nuance like that which is the difference between them being effective vs. consistently hittable.
Or, he is tipping pitches.