Folding the nut straight... too weak?

[diconoclastx]

Does anyone fold this turn because of the possible flush on the board and considering that 3 others called the flop.

***** Hand History for Game 2364027842 *****
NL Texas Hold'em $50 Buy-in + $5 Entry Fee Trny:13934459 Level:1 Blinds(10/15) - Thursday, July 14, 19:25:58 EDT 2005
Table Table 12379 (Real Money)
Seat 2 is the button
Total number of players : 9
Seat 1: glt33 ( $1000 )
Seat 2: JATC3 ( $1340 )
Seat 3: HERO ( $1050 )
Seat 4: SirRapealot ( $1025 )
Seat 5: NickCigich ( $890 )
Seat 7: RandyRiver3 ( $1010 )
Seat 8: AggieMark ( $970 )
Seat 9: Robohog ( $1090 )
Seat 10: xins0mx ( $1625 )
Trny:13934459 Level:1
Blinds(10/15)
** Dealing down cards **
Dealt to HERO [ 6d 7c ]
NickCigich folds.
RandyRiver3 folds.
AggieMark folds.
Robohog folds.
xins0mx calls [15].
glt33 calls [15].
JATC3 calls [15].
HERO calls [5].
SirRapealot checks.
** Dealing Flop ** [ 5d, 4d, Kc ]
HERO bets [45].
SirRapealot calls [45].
xins0mx folds.
glt33 calls [45].
JATC3 calls [45].
** Dealing Turn ** [ 8d ]
HERO bets [200].
SirRapealot raises [400].
glt33 folds.
HERO folds.