You granted all members of Editors access to the file manager. This allows them to upload, delete, and use the files within the pages.
By default, they are only going to see their own files. This can be handy if you, the admin, want to upload system files that a normal user isn't supposed to see. However, if you want to manage the page content using the admin account as well, you might have to allow any user to see all files. In this case, you simply set Search Files to All.