I have a John Deere MX8 bushhog on a 70hp tractor. It will not cleanly cut pigweed. Leaves a 3 to 4ft tall pyramid of stalks right in the center of my bushhog strip. So I have to bushhog everything twice. Anyone else have this problem? My blades are sharp. It cuts all other weeds and grass fine on one pass, just not pigweed. At this point I'm thinking about getting another brand of bushhog. Suggestions? Thanks