One option is to boot into Safe Mode. Restart the machine while holding down the Shift key. Booting, into Safe Mode initiates a series of maintenance routines that will sometimes clear issues. Safe Mode also temporarily disables third party extensions and plugins that can cause trouble. While in Safe Mode see if the machine runs better. Now restart again in normal mode and check.
If that doesn’t help then try installing the update again. I assume your are talking about the security update that was released a couple of days ago?