Costco Wholesale Corp. stock COST is down 2.5% in premarket trades after the retailing giant said its U.S. core March comparable stores sales grew by 2.6%, excluding impacts from changes in gasoline prices and foreign exchange. Analysts at Stifel said the core figure missed the Wall Street consensus estimate of 3.9%. Costco’s total same-store sales fell 1.1%, the first monthly same-store sales drop since April 2020. Stifel reiterated a buy rating on the stock but said the miss amounts to a “watchpoint for most retailers as Costco likely continues to outperform many peers.” Costco’s weakness in sales of non-foods “is…