Dollar General shares tumbled on Thursday after the discount retailer slashed its sales and profit guidance for the full year, suggesting its lower-income customers are struggling in this economy.Shares of the retailer which caters to more rural areas tumbled 20% in premarket trading following the earnings report.The company now expects fiscal 2024 same-store sales to be up 1.0% to 1.6%, lower than prior outlook for a 2% to 2.7% increase. Earnings per share for the year is expected to be in the range of jus ...