Shares of Dollar Tree are foundering today on the 1-2 punch of a management shake-up and a brokerage downgrade. After Friday's close, the discount retailer reported that its Chief Financial Officer Kent Kleeberger turned in his resignation, effective October 26 (by my calculation, that's not 2 weeks' notice). While his former company scrambles to replace him, Kleeberger will take on the role of executive vice president/CFO/treasurer at Chico's FAS (CHS). His expected start date is on or around November 5.

This morning, long before the opening bell rang, J.P. Morgan reduced its rating on the stock to underweight from neutral. Covering analyst Charles Grom said that with DLTR rising 24.5% already this year to date, its valuation may be getting a little steep.

Grom noted that the news of Kleeberger's unexpected resignation adds another layer to our mosaic that maybe the upside from this initiative is less robust than many suspect. He also expressed concerns that higher food and fuel costs could impact spending levels, especially among low-income households.

In late-afternoon trading, DLTR shares have given back about 3.5% on heavy volume. At its intraday low, the stock was off almost 10% but rebounded from support at its 20-month moving average. DLTR has not endured a monthly close beneath this trendline since January 2006.