Warren Buffett’s Berkshire Hathaway made a series of tweaks to its sprawling stock portfolio last quarter, including adding a financial stock during the recent banking crisis, according to a new regulatory filing. . The Omaha-based conglomerate added a new stake in Capital One Financial worth more than $950 million in the first quarter, filings show. The McLean, Va.-based financial institution has fared relatively well amid the recent banking turmoil, with shares up more than 3% in the first quarter. It was unclear whether Buffett, or one of his investing lieutenants, Todd Combs and Ted Weschler, who each manage about $15 billion for Berkshire, bought the stock. The “Oracle of Omaha” has recently been downbeat about the health of banks, saying we’re not done with bank failures and that U.S. banks could face more turmoil ahead. Berkshire Hathaway also slightly increased its two largest holdings — Apple and Bank of America — in the first quarter. The group also increased its bet on HP.