[Double Down]

I think it's a good fold. With your small bet on the flop of 50 into a 150 pot, it looks like you're the one on a flush draw. I think the first player called you with possible flush draw and a pair and then second player had the nut flush. I believe he has the nuts because if EITHER player had a good hand on the flop (small flush, 2 pair, set) then your bet would have definitely gotten raised. The only made hand that WOULDN'T raise is the flopped nut flush, because he's hoping that another spade will come on the turn and you'll make your flush. With your small bet on the turn (150 into 300), I think the first guy was making a move on you trying to pick up the pot, reading you and the utg as both still on flush draws. But with such a large bet, he was committed and now the utg can push his nut flush knowing it'll get a call. Good fold, the utg flopped the nuts.