The stock market flirted with breakeven levels the whole day on Tuesday, as the three major indexes each ended nearly unchanged. While the day was light on news, investors in Cognizant Technology Solutions Corporation (NASDAQ:CTSH), Coach (NYSE:TPR), and Valero Energy Corporation (NYSE:VLO) saw their fair share of action, as the stocks ended as three of the worst performers in the entire S&P 500 Index (SNPINDEX:^GSPC). The S&P, for its part, gave up less than 1 point, or under 0.1%, to finish at 1,950.

Shares of New Jersey-based Cognizant Technology Solutions plunged 4.7% on Tuesday, after a Susquehanna analyst downgraded the stock from "positive" to "neutral" this morning. The IT firm has been growing its top-line figures at breakneck speeds since 2009, never failing to increase revenue by less than 20% annually. But today's downgrade, combined with insider selling that has investors wondering if management knows something they don't, sent shares lower. Cognizant's Steven Shwartz, EVP, Chief Legal & CAO, completely liquidated his stake in the company last week, while a top marketing executive also sold about 85% of his shares the same day.

Source: Coach.

Coach lost 3.1% on Tuesday, as Wall Street continues to be disillusioned with the luxury goods company. One of the biggest issues facing Coach today is a fast-approaching rival, Michael Kors, which is steadily stealing market share from the iconic handbag maker. But in its effort to combat this troubling trend, Coach may be doing itself even more harm, slashing its prices and diluting its powerful brand. Branding power and margins are the name of the game in luxury, so widespread discounts at its traditional stores and a willingness to embrace outlets have investors rightfully concerned.

Finally, shares of oil refiner Valero Energy shed 2.8% today. Trading within shouting distance of its 52-week highs, Wall Street worries that the cyclical nature of the refining industry could temper the stock's upside potential. On top of that, its 1.8% dividend yield is hardly best in the biz, so it's a tough buy to justify on the basis of its income potential alone. However, as my colleague Joshua Bondy noted in a recent article, the company's conservative payout ratio means that even if the industry suffers a sudden decline, Valero is in a position to weather the downfall and maintain its dividend indefinitely.