He dropped velo after game 6 on the chart, and again after game 14, 33 and then his last 5 starts.
I'm not seeing anything that hasn't happened before.
https://www.fangraphs.com/graphs.aspx?playerid=10603&position=P&pitchgraphs=true&statArr=&legend=1&split=base&time=game&start=2017&end=2019&rtype=mult>1=15&dStatArray=FA&ymin=&ymax=