SINGAPORE stocks opened lower on Tuesday (Jul 19), tracking losses on Wall Street.The Straits Times Index (STI) lost 0.3 per cent or 8.36 points to 3,113.40 as at 9.01 am. Decliners outnumbered advancers 81 to 40 after 34.9 million securities worth S$48.3 million changed hands.Sembcorp Marine : S51 ...