Sounds like you fished in a good area.You certainly put in a long day for only 4 fish.The cold front didn't help the bite either.You said you fished bandits and harnesses.Either they weren't working or they were at the wrong depth
You should have tried spoons too or a different crank.When you went out by middle island,that water is deeper.Like 40 fow.You could have tried a weight on your cranks at that depth.Add a 2oz weight to crank should get you arround
8ft deeper.Varying the speed is good but also try some S turns or even taking boat out of gear to stall boards.Keep changing things up.Depth is most critical then speed and then color.