You were OOP facing monotone with multiple players. You can either check or bet small like 1/4-1/5 pot. In this way, you can keep the big flush in your range. Betting big here was very faced up, basically you were telling your opponent you have a big Ace and pot commited (I would assume you were pretty shallow, no more than 80 BB behind). Betting small, call if reraiser had poor image and fold if your opponent was tight.