[molotom]

I think it's very likely the K gave them a better hand than yours. The only hand you beat is a draw that called the flop then spiked a K for one-pair, but then they don't have much reason to raise you (they still have their draw after all). Also you have a read that they've done this before with a very strong hand. It sucks but I think it's a fold.

I would definitely bet more on the flop here. This is one of the situations where I would even consider an overbet. You almost certainly have the best hand but there are many straight/flush draws out there. Also when there are 6 players to the flop, you know you are playing with experts so it's particularly likely that a weak bet will induce a cascade of calls.