Generic App Icons since 10.3.1 latest update

My App icons for Mail, Photos and Messages and Notes are now 'generic' since my latest upgrade. There are a couple of third-party apps doing the same, but I can live with that.They are generic in the Dock, Launcher yet if I open the Applications Folder through Finder, some of the apps (Mail for example) have the right icon, but launching it or adding it to the Dock by dragging returns it to a generic icon!!

I have gone into Terminal and performed a 'Killdoc', rebooted/restarted and the problem is still there.

This is a real pain. Any solutions?

Thankyou.