“Downton Abbey” whiz Julian Fellowes has joined a stream of talent that has dropped out of a proposed musical version of “Slumdog Millionaire,” we hear. Fellowes was in the mix to take over the show after Danny Boyle, the movie’s director (and mastermind of the Olympics opening ceremony) and Simon Beaufoy refused to participate after producer and TV mogul Paul Smith wouldn’t hire the hit film’s full creative team. A.R. Rahman, composer of hit ditty “Jai Ho,” then said he wouldn’t let his tunes be used if Boyle wasn’t at the helm. Then replacements in talks to fill creative roles, including “Ghost: The Musical” director Matthew Warchus, fled over the brouhaha. Fellowes’ rep didn’t get back to us.