AJ played too weak?
 

Party Poker 1/2 Hold'em (9 max, 8 handed) converter

Preflop: Hero is CO with A[img]/images/graemlins/spade.gif[/img], J[img]/images/graemlins/club.gif[/img].
UTG calls, <font color="#666666">1 fold</font>, MP1 calls, MP2 calls, <font color="#CC3333">Hero raises</font>, Button calls, SB calls, <font color="#666666">1 fold</font>, UTG calls, MP1 calls, MP2 calls.

Flop: (13 SB) J[img]/images/graemlins/spade.gif[/img], 7[img]/images/graemlins/spade.gif[/img], 3[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(6 players)</font>
SB checks, UTG checks, <font color="#CC3333">MP1 bets</font>, MP2 folds, <font color="#CC3333">Hero raises</font>, <font color="#CC3333">Button 3-bets</font>, SB calls, UTG folds, MP1 folds, Hero calls.

Turn: (11.50 BB) 5[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(3 players)</font>
SB checks, Hero checks, <font color="#CC3333">Button bets</font>, SB calls, Hero calls.

River: (14.50 BB) K[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(3 players)</font>
SB checks, Hero checks, <font color="#CC3333">Button bets</font>, SB folds, Hero calls.

Final Pot: 16.50 BB

Button is a calling station who rarely raises pre-flop. He is not a very aggressive player. SB is a maniac low on chips who could have anything.

Re: AJ played too weak?
 

Given your passive read on button I guess it's OK.
I'd normally bet the turn here, but then if you get raised what do you do on the river UI? I really don't know.