They most likely are tacked on. Look really closely in the corners and down the sides, about 1/4" to 1/2" from the edge. Take a paint can opener (the kind with the bottle opener on the other end.) and slip the curved end under the edge of the grill. Lift straight up with some grunt. Don't try to pry them up or you'll dent the edge of the front frame. Replace with adhesive hook and loop fasteners squares.