The Brushes "Push" against them to maintain electrical contact.
(Oichan' s Picture Below, "After" ["Shaving" he called it].)
('Second picture is the "Before".)

In your picture of your "Bad" Brushes,notice how one is Much More Worn than the other?
'Did you have a chance to inspect the Slip Rings on your Alternator for wear,
when you replaced the Regulator?

Attached Thumbnails

   

__________________
'84 300SD sold
124.128