I would say you were trolling too fast.In December the water was a little warmer and could have trolled 1.3-1.6mph,but now with water temps around 34 degrees I would say speed 1.0-1.4mph speeds.You can also trigger bites by making more turns or driving in an S shape.That causes the lures to speed up and slow down.The lures also move up and down in water column and can trigger strikes.With weights,this movement is even more pronounced and can have lures flutter down when the boards literally stall.