iMac password stopped working, Apple Persistent State Encryption shows a recent modified date
What is "Apple Persistent State Encryption"


  Used by the persistent state feature to encrypt window snapshots to
  ensure privacy. 
  
  It is changed frequently.


So that one is normal.

As for your password, no one can change it without knowing the old password. If you have set up your log in with Apple ID assistance you can use it to recover your password. Read more here.