ok so having raised 4 times in a row, this would be the perfect time to make a raise here again, being on the button they might just think your running the table over and make a resteal or just play back at you in general.. tight players generally wont make big steals or play back at you without a hand, so your idea of them sensing weakness and raising isnt correct, would be correct against a loose bully maniac type... the only time you can jusify slowplaying kk or aa in a sng is when your a shortstack and your looking to create action. even then, on the button with under 10 bb's its a shove for me, i would slowplay if there was 8 or so people at the table and i was in early position, id limp with kk or aa looking to get raised.
as it stands you have no idea where your at and are forced to guess, two tight players betting, and your on the bubble which is a consideration, if you fold you remain at 20 bb with a big chance of hitting the money. so its up to you, but if you feel you can outplay your opponants then i would suggest folding(especially as the guy with 1800 is lower, and could be busted out this hand) especially against two tight players on the bubble who can be easily exploited.
the problem you face though is that your right you didnt show any strength preflop (a good player may see the call as strength, but we can assume they are bad, playing tight on the bubble) he could easily be raising a queen here thinking its good running a bluff betting a flush draw etc. there are times and places where its good to slowplay kk or aa preflop, but this isnt one of them.