Tiffany & Co.’s quarterly net income fell 30 percent to $63.2 million, or 49 cents per share, as the jeweler was stung by a higher-than-expected tax rate, ongoing economic weakness, and high prices for precious metals and diamonds. Tiffany also cut its full-year earnings forecast. It now expects 2012 earnings of $3.20 to $3.40 per share. Its prior outlook was for $3.55 to $3.70. Tiffany expects better results during the holidays in part because of new stores and new products.