I performed a cook of 2 racks of Memphis style ribs using a 1.7 oz. chunk of Weber Firespice apple wood. The ribs were cooked in my Smokette SM025 for prox. 4 hrs. at 225 degrees. I used a dry rub consisting of 1/2 cup kosher salt, 1/2 cup black pepper, 1/4 brown sugar. To my dissappointment they turned out somewhat bitter. What might I have done wrong?