25/50 blinds 10 antes, no reads on villain

everyone is roughly 200bb deep.

I'm utg with KsKd, I raise to 225 , 2 callers both in position.

flop: 3h 4h 7d

I bet 500 into 800 pot, 1 fold, button min raises to 1000, i call. 

turn: 9d

I check, button bets pot 2800, i call.

river: 8s

I check, button goes all in for 6275 into 8400 pot.

hero:?

I folded and was genuinely confused. I planned on calling any non heart bet on the river, but i just froze up and folded.

Was this fold correct? What could I have done better in this hand?

BTW: when I mucked, he showed a missed heart flush draw.