CO is a huge donk and SB a decent regular and has been isolating CO a bunch. Im very confused.

$0.5/$1 No Limit Holdem
5 players
Converted at weaktight.com

Stacks:
UTG ($50.90)
CO ($27.35)
BTN ($201.35)
SB ($100.50)
Hero (BB) ($102.65)
[UTG posted $1]

Pre-flop: ($2.50, 5 players) Hero is BB
UTG checks, CO raises to $2, BTN calls $2, SB raises to $13.50, Hero raises to $31, UTG folds, CO calls $25.35, BTN folds, SB calls $17.50

Flop: ($92.35, 3 players)
SB bets $69.50