Ensure the attributes no longer exist is the Schema using the Schema Management mmc snapin.
The ADSI Provider (which is used by Active Directory Users and Computers) does perform an attribute cache:
https://msdn.microsoft.com/en-us/library/aa746499(v=vs.85).aspx
The cache file is located under:
%localappdata%\Microsoft\Windows\SchCache\<domaindsnname>.sch.
Renaming this file and rebooting the machine should clear the cache.