The final months of 2014 were more difficult for big banks than investors suspected. Bank of America and Citigroup reported disappointing results Thursday, hit by lower trading revenues and more legal expenses. That followed JPMorgan’s weaker earnings announced the day before. Shares of all three banks on Thursday fell 3 percent or more, a bigger decline than the stock market overall. Like JPMorgan Chase, Citigroup and Bank of America saw drops in their fixed-income trading revenue as client trading activity slowed. For the fourth quarter, Bank of America announced profit of $3.05 billion, or 25 cents a share, down from $3.44 billion, or 29 cents a share, a year earlier. Total revenue at Bank of America fell 12.6 percent to $18.96 billion. Meanwhile, Citigroup had a quarterly profit of $350 million, or 6 cents a share, compared with $2.5 billion, or 77 cents a share, a year earlier. Revenue was flat at $17.78 billion.