The Dow Jones Industrial Average (^DJI 0.67%) has hit the right marks for investors in 2013 with a stellar year for blue-chip stocks. But the index hasn't quite lived up to these gains recently: Over the past three months, the Dow has barely broken as earnings, Fed watching, and Washington discord have all taken their tolls on the index.

You shouldn't be concerned by the little day-to-day movements of the Dow, but the stocks that have led blue chips down between the start of July and the start of October have raised concerns around the investment community. From beverages to tech, let's take a look at the Dow's three biggest losers from the last three months -- and whether their slumps should tempt you to shake up your portfolio.

Coca-Cola goes flat
Surprisingly, one of the Dow's most legendary stocks has taken a tumble in the past quarter. Coca-Cola's (KO 0.63%) shares have slipped since 2013's second half kicked off: The stock lost 5.4% between July and October. The stock took a hit in mid-July after the firm's profit declined 4% in the second quarter, and investors have questioned Coca-Cola's beverage volume growth in Western economies as Europe and the U.S. have pushed back against carbonated soft drinks.

That declining investor optimism led to a long slump through August, but don't be too quick to run away from this stock. Coca-Cola's long been one of the Dow's most iconic stocks for a reason, and the firm's exploring new avenues for growth and expansion even as its reliable markets waver. Emerging markets feature populations that still consume far less in Coke product servings per year than the populations of developed economies. Americans, for instance, consume more than 10 times more of the company's product in each year than residents of China.

The firm's operating margins have also risen in valuable markets such as Latin America and Africa in 2013, a key that Coca-Cola will need to continue tapping into as Europe and North America cede importance in the firm's pecking order. While Coca-Cola will likely see a bumpy road in volume growth in the U.S. and Europe as it pushes its growing noncarbonated products, emerging markets and global growth offer plenty of upside to this stock despite its recent slump.

Intel (INTC 0.61%) has performed even worse, losing nearly 5.8% between the start of July and October. Intel's working hard to diversify away from the declining PC segment, and that transition's taken a toll on this stock over the past 12 months. The firm's sales projections for the third quarter didn't help the stock bounce back recently, as Intel has already recorded four straight quarters of falling revenue.

Yet even some of Intel's innovative ideas are stalling out. The company's plan to dive into the Internet TV business hit a snag recently as the firm delayed the venture until next year in order to look for partners. The TV expansion is questionable as it is -- it's a rather dramatic departure from Intel's core business, and the firm's staring at tough competition. Intel's gains in its data center business have been promising, but until the company can advance strongly into higher growth fields such as mobile to counter its PC division's plunging prospects, stay cautious with this troubled tech stock.

Even Intel's troubles haven't matched up to Verizon's (VZ -4.67%) over the past three months. America's top wireless provider saw its stock slide a painful 6.6% between the start of July and October. Telecoms have taken a hit lately -- top rival AT&T has also toughed out sliding shares -- but Verizon's slide is no reason for you to hit the "sell" button. If anything, it's a great dip to pick up a stock poised to run higher based on its recent moves.

Verizon's ballyhooed buyout of Vodafone's share of Verizon Wireless has caught the attention of every corner of Wall Street since the deal was announced. It's for good reason: Verizon's poised to grow its lead on AT&T in the U.S. wireless battle. The firm's looking beyond just phones, however. The company announced this week it will expand its cloud business to offer new cloud infrastructure and storage services. Verizon's looking to square off with the top names in cloud service providers such as Amazon, and while the competition's fierce, Verizon's ambition and willingness to look at the big picture are promising signs for investors wary of the stock's slide.

Verizon's cloud push is a situation to keep an eye on, but for the long term, this stock's dip since July isn't a concern, but an opportunity.