Although we don't believe in timing the market or panicking over daily movements, we do like to keep an eye on market changes -- just in case they're material to our investing thesis.

The S&P 500 Index (^GSPC 0.87%) fell again today, losing 9 points, or 0.6%, to end at 1,646. Consumer sentiment dropped in August, and markets continue to bet on higher interest rates ahead of the Federal Reserve's much-awaited meeting in September. While more than 70% of S&P stocks fell today, there were three stocks in particular whose losses were truly exceptional Monday.

Cliffs Natural Resources (CLF 0.19%) was one of the absolute worst performers in the index, dropping 4.8% Monday. The stock has lost more than 11% in the past five days of trading alone, and that negative momentum didn't get much help today from Morgan Stanley, as one of its analysts cited higher supply of iron ore, an escalating cost of mine maintenance, and downward-trending price outlooks for the material next year. That trifecta of issues could mean further turmoil still lies ahead for Cliffs investors.

Shares of oil explorer Apache (APA 0.34%) also lost out big-time on Monday, shedding 4.6% as the political disruption and uncertainty in Egypt continue to rise. Stifel Nicholas downgraded the stock today, as the investment house noted that nearly a quarter of the company's free cash comes from Egypt. Apache shares, too, have been on the down-and-out, posting losses for the past five days as violence in the Middle Eastern country spirals out of control. 

Lastly, shares of life-insurance company Genworth Financial (GNW 0.33%) tumbled 4.5%, though there wasn't much in the news to spark the sell-off. Genworth CEO Thomas McInerney has hinted recently that prices of long-term care insurance will probably be on the rise in the future, a fact that could drive some customers to the increasing pool of competitors. However, the long-term-care insurance market is nearly an oligopoly at this point, so Genworth might be able to get away with higher prices, at least for the time being.