It started off with Walmart (WMT). Last week, at a meeting with analysts, the company predicted that sales would be flat this year and that earnings would likely drop this year and next. Walmart’s stock fell 10%, or $6.07. Buffett’s Berkshire Hathaway (BRKA) holds roughly 60.4 million shares of Walmart, so that was a $360 million hit to the conglomerate’s investment portfolio.

That same day, Wells Fargo (WFC) reported earnings that were up a mere 1%. Banks are supposed to do well when the economy is doing well. Its shares dropped a modest $0.36. But to Buffett’s Berkshire, which holds 470 million shares of Wells Fargo, amounting to a $24 billion stake, that small drop meant another $170 million shaved off the Oracle of Omaha’s portfolio.

Then came IBM (WFC), which Buffett has bet heavily on over the past few years. On Monday afternoon, the tech giant reported third quarter earnings that were 14% below the same quarter’s results last year. IBM’s shares fell 6%, or $8.58. The resulted in a $680 million hit to Buffett’s Berkshire, which owns nearly 79.5 million shares of IBM, a stake now worth just over $11 billion.

Three stocks, one week, $1.2 billion down the drain.

These are only three of the dozens of stocks that Buffett and his two top investment lieutenants, Todd Combs and Ted Weschler, have in Berkshire’s portfolio. Others have likely risen. And Wells Fargo has since rebounded. What’s more, Berkshire’s portfolio is roughly $115 billion, so a $1.2 billion drop is only a loss of 1%.

But they are three of the top five holdings in Berkshire Hathaway’s stock market portfolio, as of the end of the second quarter. The other two are American Express (AXP) and Coca-Cola (KO). Together, those five stocks make up 60% of Buffett portfolio.

Taken together as a group, Buffett’s five largest investments come across as struggling giants with business issues that don’t seem to be going away soon, the kind that will be very hard for the companies to fix. Coke needs to make a massive shift away from sugary drinks. Walmart still lags in e-commerce at a time when retail is shifting online. And American Express, which has lived off corporate expense plans, is struggling as companies cut back costs. The end of its Costco deal will stymie efforts to reach new customers.

Even IBM, Buffett’s most prominent investment in the technology industry, seems behind the times. It’s trying to make the shift into business analytics and cloud computing. But its supercomputer Watson has yet to generate significant revenue. And its traditional services business is slipping. At the very least, Buffett’s timing seems to be off with IBM. In the five years before he started buying shares in the company in early 2011, IBM’s stock was up 78%. Since then, the company’s stock price has fallen by just under 4%.

Doug Kass, a hedge fund manager who has long been bearish on Berkshire, recently wrote that Buffett has hit his peak. He says Berkshire has put its money in companies that are “poorly positioned in our changing economy.” Kass says the company looks like an index fund that’s stuck in overpriced, slow growing companies.

Berkshire’s shares decreased by more than 11% in 2015 so far. At the same time, the S&P 500 has been basically flat. Of course, this comes after a number of years in which Berkshire’s shares have far outperformed the S&P 500.

Berkshire, though, has morphed in the past decade or so from Buffett’s insurance-investing vehicle to a full fledged conglomerate. It now owns the giant railroad Burlington Northern Santa Fe, a quarter of the food company Kraft Heinz, Fruit of the Loom, Dairy Queen, and dozens of other companies. In August, it said it was buying Precision Castparts, a maker of industrial equipment, for $37 billion, its second largest deal ever, after BNSF. So, the performance of its public investments now constitutes a shrinking part of what determines the movement of its stock price.

But here, too, Kass says Buffett is overpaying for slow growing businesses that generate a lot of cash flow and not much growth. I have written about the fact that Buffett has been paying higher and higher prices for Berkshire’s acquisitions. Berkshire paid 25 times earnings for Kraft, a company that was only expected to grow its earnings by 8% a year.

It’s a dangerous business to second guess the greatest investor of all time. But here’s the bear case for Buffett, if you want to make it: Buffett has generally favored business that have a lot of value in their brands. That generally puts him into large established companies that have dominated their industries for a while. Buffett is a buy and hold investor, and he thinks of himself like an owner. He has no plans to sell his biggest investments.

If we are living in a time of with massive economic change or a big shift in society’s preferences, someone who invests like Buffett will get caught off guard.

That being said, everyone has a bad week, even Warren Buffett.

Correction: An earlier version of this story said that Berkshire Hathaway held 40 million shares of Wells Fargo. In fact, it holds 470 million shares.