The running back position has seen its share of troubles this season.
Crowell, the team leader with 724 yards rushing on 145 carries and five total touchdowns, was suspended for the first quarter of the Vanderbilt game for unspecified reasons.
Thomas, who has 44 carries, 206 yards and two touchdowns, missed the season-opener for a violation of team rules.
Malcome, a redshirt freshman who has one career carry, momentarily left the team in September before deciding to rejoin the squad.
The position is already thin due to junior Richard Samuel's ankle injury. He'll miss at least four weeks after surgery.
The only tailbacks remaining on roster with a carry this season are former walk-ons Brandon Harton (11 carries for 34 yards) and Wes Van Dyk (one carry).
"We have certain standards in all that we do and their actions do not reflect the Georgia way," Richt said in a statement. "They will serve their suspensions, learn a lesson and I'm sure be better men for it."