Anyone muck this flush?

[La Brujita]

First hand of a Party $30 I am in the big blind with 9h 3h and get a free play.

Flop comes 2h 7h Th four handed. I check looking to check raise and next to act bets 200 one fold and one cold call.

This was the moment of decision for me. I obviously wanted to make it expensive for a singleton Ah or Kh or any two pair or set. What is a huge worry is a cold call by the second in the pot.

Added to my uncertainty is in a $30 game usually with a few truly loose players, you can never know what anyone is holding with any certainty.

I raised all in and was drawing dead to a Q high flush (the cold caller). First to act had 2 pair.

Was my play terrible, or average? In my opinion it was one of those hands I where I just shrug my shoulders and say next game.

Also, how bad do you think the flat call was by the Q high made flush? I would push in in a second here to make the singleton A or K have to pay. After all 200 is 25% of the stack.

If you made a king high flush would you flat call? I might well there.

Any thoughts, opinions welcome.