Yes, the problems that befell Chelsea last season did affect the team, so their performance decreased slightly. Although many say "it shouldn't lower their performance" But we don't know for sure what happened to the team as a whole. Because what we know is what appears on the outside. It's very difficult for Chelsea to stay optimal in these circumstances.
What is certain is that Chelsea will continue to try to improve their performance at the beginning of next season even though what appears from the outside is a decline in performance because it is triggered by problems that existed last season. But overall Chelsea are still trying to make his team's performance improve next season.
Actually they are not yet fully stable, because they still need time to be able to restore something that was lost after the problems they faced. At least now it's much better than last season, and now they're starting to come back with something new. After all they are one of the big teams that are expected to give their best performance.