Shares of Green Dot Corp. are down 2.8% in premarket trading Monday after BTIG analyst Mark Palmer lowered his rating on the stock to neutral from buy. “Green Dot’s recent record of strong operational performance, highlighted by a return to organic growth in its core prepaid debit card business and the launch of a variety of new programs and partnerships, has enabled its stock price to double in less than a year,” Palmer wrote. “As a result, Green Dot now commands a valuation that we believe fairly reflects the company’s growth trajectory and future prospects.” Green Dot sells prepaid debit cards, which have become hot in recent years. However, Green Dot has picked up some new competition lately, from PayPal Holdings Inc. and Mastercard Inc. , Palmer wrote. The stock has gained 30% so far this year, while the S&P 500 has ticked up 4%.