Yes, they did. But some pitchers got off to incredibly good starts this year. Chapman, for example had an ERA of 0.39 on June 6, with an absurd 43 K's in 23 innings. After Stickygate he fell off a cliff.
We know that they also changed the baseballs this year, reportedly with higher seams. So I would speculate that the combination of state of the art sticky stuff and higher seams had a lot to do with some of the amazing starts.