S&P Global Ratings is downgrading the credit ratings of five banks, including some of the nation's largest lenders. The credit agency pointed to "tough operating conditions" that are straining the banking industry and also lowered its rating for two other banks. In explaining its rationale for the downgrades, S&P noted in a report on Monday that banks are facing risks that could make them "less resilient than similarly rated peers." The move comes only two weeks after Moody's cut the credit ratings of 10 small and midsize banks because of growing financial risks and strains that could erode their profitability.