overs on low board facing aggression

Reads: MP is fairly tight and a good player. Me and him have been feeding off a fish that was putting on a bad beat clinic earlier. Button is also a somewhat decent player, he hasn't been at the table for too long so I don't really have an idea of his ranges.

PokerStars No-Limit Hold'em, $0.10 BB (5 handed) FTR converter on zerodivide.cx

Button ($20.70)
SB ($16)
BB ($4.60)
Hero ($23.25)
MP ($38.75)

Preflop: Hero is UTG with J[img]/images/graemlins/heart.gif[/img], J[img]/images/graemlins/club.gif[/img].
<font color="#CC3333">Hero raises to $0.5</font>, MP calls $0.50, Button calls $0.50, <font color="#666666">1 fold</font>, BB calls $0.40.

Flop: ($2.05) 9[img]/images/graemlins/diamond.gif[/img], 6[img]/images/graemlins/club.gif[/img], 2[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(4 players)</font>
BB checks, <font color="#CC3333">Hero bets $1.4</font>, MP calls $1.40, Button calls $1.40, BB folds.

I figured a 3/4 pot bet might take it down considering the low flop. I didn't really expect two callers.

Turn: ($6.25) 3[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(3 players)</font>
<font color="#CC3333">Hero bets $2.1</font>, MP calls $2.10, <font color="#CC3333">Button raises to $4.2</font>, Hero ???

The 3 seemed like a harmless card, I doubt either of them would have called both bets with 45s. I was thinking maybe one of them had a/9s, overs, maybe a set of 9's or 6's. The min raise does seem a little wierd though.

I was completely lost here, anyone have a good line for this situation?