I would guess the issue is caused by some 3rd party plugin that you are using. Either this plugin handles something different on profile pages of admin users or you happen to have something on this admin profile page (widget / widget content / profile fields) only that uses some css not used on other profile pages. My first guess would be profile manager or widget manager plugins, if you use any of these. Try to disable 3rd party plugins to identify which plugin is causing the issue. To be on the safe side regarding cached items, I would suggest to als0 refresh the site cache in the admin area after disabling some plugin before reloading the profile page to see if the css is displayed correctly.