Don’t mess with Standard & Poor’s. The credit agency cut its long-term credit ratings for 15 banks Tuesday, including U.S. institutions Bank of America, Citigroup, Goldman Sachs, Morgan Stanley, and JPMorgan Chase. The one-grade lowering comes after an overhaul of the method used to grade banks—because of criticism for its slow response during the 2008 crisis. A few months ago, the agency Moody’s downgraded Bank of America, Citigroup, and Wells Fargo. Bank of America’s stock plummeted Tuesday, nearly falling below $5. If the bank reaches that new low, many think investors will quickly sell, further damaging the bank.