Guys, please read this tell me if you can see if / what I did wrong.

This happened around 1am on party poker.

No limit table..

I hit 67s from the big blind.

4 people in for $.50 on the flop.

Flop comes 543 (rainbow) I flopped the nut straight.

I check
Player 1 bets the $2
player 2 raises to $4,
player 3 folds..
I called the $4
player 2 calls the raise

pot = $8

A bit of slow play here, probably where I made my mistake. At this point I'm thinking player 1 is on a small pair, maybe a draw. I'm thinking player 2 is on top pair maybe two pair. (he's a bit agressive with top pairs)
Turn comes it’s a K (4 suits on the board, no flushes coming out)
I'm thinking its money for me because it could really help someone out.
I check it
Player 1 checks
player 2 makes it 8
I raised it to $16
Player 1 calls the bets (not sure what he was doing I thought he hit two pair
Player 2 calls the 8

pot = 55ish

Nice pot I've got the nuts with two callers. I'd rather it be heads up but I'll play it like this
River comes another King..

I'm worried now because I was thinking player 2 hit two pair with the king on the turn. Not too sure about player 1. At this point i'm along for the ride. I bet out all-in!!!! (at this point I only had like 20 left in front of me. My bet was 1/3 the pot.
Player 1 called it
Player 2 called it

That’s when I knew I was in trouble. No way both of them missed it.

Player 1 had 3-3 in his hand for a 3-k boat.
Player 2 went runner runner with k-4 for the boat.

1 darn card.. They had one out to beat me.

Now my question is, did I play this wrong or did I end up with a bad beat.

I'm leaning towards bad beat, but I also let draw for their hands. so I'm confused.

how would you guys have done it?