Source: Wikimedia Commons.

The European Central Bank moved forward on Thursday with a much-anticipated plan to introduce new stimulus measures to foster economic growth on the continent, and stocks both in Europe and in the U.S. generally reacted favorably. With an 18-month plan to spend 60 billion euros per month on asset purchases, the ECB has committed more than 1 trillion euros toward getting its economy in line. Partly in response, the Dow Jones Industrials (DJINDICES:^DJI) gained nearly 125 points shortly after 11 a.m. EST. Yet even as the Dow climbed, some of its component stocks fell precipitously, with American Express (NYSE:AXP) and telecom giants AT&T (NYSE:T) and Verizon (NYSE:VZ) leading the decliners.

American Express fell 4% as the company's fourth-quarter earnings report gave a mixed picture of the card pioneer's future prospects. Overall, AmEx's revenue climbed 7% from year-ago levels net of interest expense, while net income climbed 11% and earnings jumped to $1.39 per share. Yet even though cardmember spending rose 6%, much of those revenue gains came from AmEx's sale of its stake in Concur Technologies, which raises concerns about the sustainability of the card company's growth rates. Moreover, loss provisions rose 25% from year-ago levels, and declines in net income from its core U.S. Card Services and International Card Services divisions showed that AmEx still faces challenges in keeping its margins up. That partly explains AmEx's decision to cut about 4,000 jobs, or about 6% of the company's workforce, but investors are clearly worried about whether that will be enough to keep the card company competitive with its rivals.

Meanwhile, Verizon was down more than 2% after reporting its own financial results for the fourth quarter. The wireless giant added 2.1 million net retail connections during the quarter, but necessary pension revaluations and adjustments sent the carrier to a net loss of $0.54 per share during the period. On an adjusted basis, Verizon weighed in with earnings of $0.71 per share. The company's 2015 guidance included sales growth of about 4% for the coming year, but rising churn rates showed the ultra-competitive nature of the wireless business right now as rival carriers fight a bitter price war to try to draw customers away from each other. That realization helped send AT&T down in sympathy by about 1.5%, and with that carrier releasing its own quarterly financials next week, investors will get another data point to assess the overall health of the telecom industry.

Today's moves show that even as markets react to broad-based macroeconomic moves, individual companies don't react uniformly to the news. If you stay aware of the specific issues that each stock you own has to deal with, you'll do a better job of choosing investments that will behave the way you want in the face of whatever challenges they have to overcome.