Actually, it is fair... They became Masters after they entered said tournaments.
So the Master that is leading the Pro tier event, was a Pro when he entered. What makes the playing field level is that he is only allowed to use Pro tier equipment when playing in a Pro tier event. Therefore he has no advantage over anyone, as the clubs he used are clubs any Pro could go out and purchase in use in these events. Same holds true for the amateur - he is only able to use amateur level equipment in amateur events.
From this point on, any new tournaments they enter will be as Masters.
Hope that helps. Good Luck.