A few highly rated stocks bucked market weakness Thursday and scored new highs in heavy trading. Signet Jewelers (SIG) rallied 8.34, or nearly 8%, to 116.37 in five times average trade. Thursday marked its best performance in six months. Signet gapped above a 113.28 buy point from a flat base. Before Thursday’s open, the operator of Kay Jewelers and Jared The Galleria of Jewelry reported second-quarter earnings of 72 cents a share ex items.