Preflop
A raise to 4BB is not normal and especially not with stacks as shallow as around 20BB. And while K9s is usually a standard defend, when the opponent goes this large, I think, you can just fold. My general read is, that such an oversized raise is almost always a strong hand, that the Villian is willing to go with, if they get 3-bet.
hands like AJ+, KQ, 88+. Against such a range K9s is not in good shape, and you are getting a bad price out of position.
Flop
You flopped the second nut flushdraw, and even before any action takes place, you should realise, that you are committed to the pot with only around a pot sized bet left. Which by the way is something, you should think about before sticking in the call preflop. If for instance the flop had come K74 with 2 diamonds instead of J74 with two hearts, you can also not really get away with so little left behind.
And since you are committed to this pot but dont have a made hand yet, I actually like a donk shove here rather than the traditional check to the preflop raiser. If they both missed with hands like AK, AQ, AT, KQ etc., then there is a good chance, you can just take it down right here and now. And if you get called by a hand like AJ or QQ, its essentially a coin flip.
Calling preflop and then donk shoving the flop is also known as the stop-and-go play. Its kind of an old school strategy, but in my experience it still work reasonably well in online micro and low stakes games. And even if LJ is good enough to understand, that your range is almost entirely made up of draws, then what is he going to do about it? Call you with AK, when he still has another guy left to act behind him?
This is not, what you did however, and unfortunately both opponents decided, that they also want to go with their hands. This is not ideal, since now you have very little fold
equity against LJ and none against BTN, and you hardly ever have the best hand, so you are basically just hoping to get there. But you are getting around 3:1, and for that reason you still need to call it off.