You can do them in any order, but you have to hit them until you hear a clicking sound instead of just metal-on-metal. It'll take a different number of hits for each one. I can't remember what the reward is, though. Probably a HP-up?
Ed: oops, I didn't see your parenthesis. If they all clicked, maybe you missed one? I think there are four or five in total. Also, the door they open is at the bottom left of one of the rooms, IIRC. (There is a wall to break at the top right, though.)