The S&P 500 remains in an uptrend and hit a new high on Monday, but some key groups are showing signs of selling pressure in April. The PerfChart below shows month-to-date performance for the S&P 500 SPDR (SPY), the Equal-Weight S&P 500 ETF (RSP), the Equal-Weight Consumer Discretionary ETF (RCD), the Retail SPDR (XRT) and the Home Construction iShares (ITB). SPY and RSP represent the broader market and both are up in April. Even though the broader market is in good shape, the consumer discretionary sector is down 2.46% and under selling pressure. Weakness in this key sector can be attributed to housing and retail. Notice that ITB is down over 8% and XRT is down over 4%. Chartists should keep an eye on these three groups because they are important barometers for the domestic economy. Further weakness in these three could extend to the broader market and lead to a correction.