Web applications (WordPress, Drupal, etc.) that are out of date can contain bugs that significan'tly affect resource usage on your hosting account. They also leave your Website at risk of compromise, which can affect resource usage as well as security.
Here are some common causes and indicators of issues related to outdated applications:
You can try to correct resource usage caused by outdated applications by following any and all of these steps:
If you are still experiencing issues with resource usage, review your hosting for other possible causes at Common causes for resource overusage (Linux).
You will want to make sure that you are correcting the underlying cause to any resource issue. Simply removing Websites and/or files without correcting the underlying issue can cause the problem to recur.