Author Bio Robin Hartill is a Florida-based personal finance writer and editor, and a CERTIFIED FINANCIAL PLANNER.™ She is a graduate of the University of Florida. The S&P 500 index finished out a volatile January up 1.01%. But hotel and casino operator Las Vegas Sands (NYSE:LVS), payment processing provider Global Payments (NYSE:GPN), and cloud-based HR management corporation Paycom Software (NYSE:PAYC), all had a January they'd rather forget. They were the S&P 500 index's biggest losers in January, with all three companies posting double-digit drops. Here's why these three stocks tanked -- and what you need to know if you're thinking about snatching them up.