ATHENS — Keith Marshall is healthy again, so Nick Chubb doesn’t have to be a one-man tailback corps for Georgia this season. After being limited by injuries to a combined eight games the last two years, Marshall is trying to return to the form he showed in 2012, when he and Todd Gurley were the star freshmen tailbacks from North Carolina. Marshall ran for 759 yards and eight touchdowns as a freshman, but he hasn’t been the same since then.