Warren Buffett is happy to admit his mistakes when he makes them-just don't remind him how much money he lost in the process.

IBM and Coke represent two of Berkshire Hathaway's (BRK-A) three biggest investments, but their operational missteps have already cost him $2.52 billion this week (factoring in Wednesday's early declines).

On Monday, Buffett lost nearly $1 billion on his third-largest investment, IBM (IBM), after the company posted disappointing earnings.

On Tuesday, Coca-Cola (KO) did the same thing , posting third-quarter revenue that fell short of expectations and warning of currency headwinds.

The losses in IBM and Coke add to a recent rough patch for Buffett, who slashed Berkshire Hathaway's (BRK-A) stake in British grocer Tesco (London Stock Exchange: TSCO-GB) earlier this month.

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He has described buying into the stock as a "huge mistake."

And to be sure, it hasn't been all bad news this week-Buffett's favorite bank, Wells Fargo (WFC), is up more than $816 million since Monday morning.