The bug is that unlike Generals, Admirals don't gain/lose Command rating for winning/losing battles. You need to edit a text file to fix the bug as described in this thread.
Oh, the reason why you got Admirals with command stars before was either that they gained one or more ancilliaries - Priest of Neptune, Seamaster and/or Shipwright - when recruited, or later gained a Navigator... all provide 1 or 2 Command stars.
Bookmarks