NL25 KK played too weakly?

[pingu]

No real reads on the villain - only been sat down for 15 hands. One of my old leaks was not value betting enough on the river, so I was trying to do that here. Comments on all streets appreciated.

Seat 1: MP2 ($26.00)
Seat 2: MP3 ($10.62)
<font color="green">Seat 4: Hero (BTN)($25.11) </font>
<font color="red">Seat 5: Villain (SB) ($23.32) </font>
Seat 6: BB ($22.38)
Seat 7: UTG ($37.62)
Seat 8: UTG+1 ($55.05)
Seat 9: UTG+2 ($0.00)
Seat 10: MP1 ($14.67)
*** HOLE CARDS ***
Dealt to iPingu [K [img]/images/graemlins/club.gif[/img] K [img]/images/graemlins/spade.gif[/img]]

*** PRE-FLOP ***
4 folds, MP3 calls, fold, Hero raises $1.25, Villain calls $1.25, 2 folds

*** FLOP *** [4 [img]/images/graemlins/heart.gif[/img] J [img]/images/graemlins/spade.gif[/img] 7 [img]/images/graemlins/heart.gif[/img]]
<font color="blue">OK, good flop for me, I'm thinking I'm way infront - Villain is SB so could have any connectors / 1-gaps so I didn't want to fold a pair out with a full pot bet </font>

Villain checks, Hero bets $1.75, Villain calls $1.75

*** TURN *** [4h Js 7h] [2h]

Villain checks, Hero bets $3.50, Villain calls $3.50

<font color="blue">So should alarm bells be ringing now? That's 3 smooth calls - I'm thinking that a set/2-pair would've re-raised by now especially with the prospect of a 4th heart </font>

*** RIVER *** [4h Js 7h 2h] [9s]
Villain checks, Hero bets $4.00, Villain goes all-in with $16.82, Hero folds

<font color="blue">Did I let a draw get there with weak flop and turn bets? </font>