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 Dow Jones Industrial Average (DJINDICES:^DJI) has added to yesterday's losses, down 40 points just before 11 a.m. EDT. Investors kept mulling over the implications of yesterday's Federal Reserve decision to keep its stimulus policy unchanged, but declines from financial stocks Visa (NYSE:V), American Express (NYSE:AXP), and JPMorgan Chase (NYSE:JPM) added to the Dow's woes this morning.

Visa has dropped 4%, and because it's the most influential member of the Dow, its $8 share-price plunge was responsible for more than 50 points of downward pressure on the average. Despite a large one-time tax provision that sent GAAP earnings lower, the card-network giant reported substantial growth in adjusted net income and revenue in its fiscal fourth-quarter results last night, including double-digit percentage gains in operating revenue from its data processing, international-transactions, and service segments. Yet, as we've seen from some other high-growth stocks lately, even healthy growth wasn't enough to satisfy investors, given Visa's expensive valuation.

American Express has fallen 1.6%. Visa's results likely had a negative impact on AmEx as well, although this morning's earnings report from MasterCard (NYSE:MA) painted a different picture of the card industry that could give AmEx bulls a better argument. MasterCard reported healthier spending levels among its customers than Visa did, with some analysts pointing to the fact that Visa has greater exposure to the U.S. card market than MasterCard, with its more international focus. Meanwhile, American Express has traditionally targeted the upscale cardholder market, and this group's spending patterns have held up far better throughout the past several years than those of the U.S. population as a whole. With shares trading at a less expensive earnings multiple than Visa or MasterCard, AmEx's price decline could give investors more of a bargain opportunity.

For JPMorgan Chase, credit cards are just a part of the company's massive financial empire. Shares dropped 1% as the bank continues to wrestle with attempts to finalize a $13 billion settlement over mortgage-bond issues from before the financial crisis. Shareholders have routinely celebrated even big-ticket settlements from JPMorgan as evidence that the bank is putting its legal liability behind it, but potential roadblocks could prevent JPMorgan from moving forward as quickly as it would like.