If you found events 4771 and 4625 in security logs, it means that account is used on other machine in your network, that try to authorize trough this domain controller, that's why you are able to login to other servers on your network in the near same time. Try to find out the source of requests in security log, then check that machine with the following:
Stale credentials for Windows Service accounts.
Stale credentials used to run Scheduled tasks.
Multiple Citrix XenApp or Remote Desktop Services sessions open when a user initiates a password change.
Users logged into multiple computers when initiating a password change.
Disconnected Citrix XenApp or Remote Desktop Services sessions that are not configured to timeout.
Administrative Remote Desktop Connections to Windows servers left disconnected.
Applications with their own credential stores that authenticate against Active Directory with stale credentials.
Please click the below link to understand more about logon Failure which leads to Account lockout: