He won something like 7/7 tie-breaks, many from 5-2 or set point down etc. Basically any set that was close he would find a way to win it, seems to have lost that ability for now.
Players don't just lose their forehand, game, or abilities in a 2 monts span (unless of course injury or traumatizing event).
Sometimes they play well, sometimes they don't, that's it. And you can't define a player's clutchness by ONE tournament. If anything Murray has proved his unclutchness many many times.