Doing the simple math, that means that there are about 7 boats still catching fish. I'd bet even money that its the same seven, right?
Time for some constructive criticism. Your post makes it sound like you need help in finding the lure or technique to get you back on the 4lber's you were catching last month, and that's wrong. The real problem has nothing to do with the lure and everything to do with location. If you are fishing the same lures in the same locations and the results have changed, it doesn't take a rocket scientist to figure out that the fish have changed and you haven't.
Time for some advice. Your tournament is only four hours long, so you need to concentrate your efforts on the limited amount of remaining cover, whether its those trees, cribs, or a patch of weeds that didn't get sprayed into oblivion. If after the first two hours you still haven't put anything in the box, put down the rods and take a boat ride. By now you should have figured out what the "lucky" seven are fishing out of, so go look for them. At less than 600 acres, it shouldn't take too long to find all of them. See where they're fishing at, mark those spots on your GPS, and then go back to those spots a day or two later, and see what those areas hold (besides fish). Once you've figured out what the "lucky" guys are targeting, make yourself some luck by finding somewhere that has the same conditions/cover/whatever that's holding fish.