Bummer for sure, Anon. You can’t lay that down, and I think your action was right. The only other option would have been to re-raise the turn – but like you said, there are 2 hands in the deck that beat you – and you were maximizing value.
Just sick to get smashed with a straight flush, esp. for $1100 in a 5/5… bummer! Hopefully you were only in for a portion of that $1100 stack, and not stuck on top or anything.. get back after it!