His velocity hasn't changed. The biggest issue I can see is that he isn't throwing his off-speed stuff for strikes as much. Who knows if it's mechanical, injury related, or between the ears / catcher / pitching coach. I suspect teams are laying off those pitches more, and keying in on his fastball.
His zone% on the curve has gone from 45.4, 42.5, 49.0, to 35.6.
His zone% on the slider has gone from 48.6, 48.9, 33.9, to 22.5.