This hand was from .50/1.00 6-max game, 100BBs effective on Bovada. I apologize for lack of colorful suit symbols. Hole cards are not available.

CO opens to 3.00, SB calls.

Flop: Qd 4d 8h

SB checks, CO checks

Turn: Qd 4d 8h 9h

SB bets 2.00 into 6.65, CO calls

River: Qd 4d 8h 9h 4c

SB bets 11.55 into 10.45, CO folds

My question is about the strength (or lack thereof) of CO's range after he checks back flop and calls a < 1/3 pot bet on the turn. Was the SB's overbet correct against CO's range, and should it have been a much bigger overbet? What other information needs to be considered in this situation, both from the CO's perspective and the SB's?