Brown had a bad game 3 (as most of the Cs did) and a bad game 6. Better at home.
Horford's been the best player for the Cs so far statistically. Horford's playing against the Freak and Brown's matched against Brogdon, a rotation player, and Snell, who sucks. Big difference.
Plus/Minus stats are controversial enough, but not useful in small samples.