Shares of Chipotle Mexican Grill Inc (CMG.N) have lost some of their luster recently and unless growth revives at the company, the stock could see a 15 percent to 20 percent plunge, the July 6 edition of Barron’s said. Chipotle’s stock could drop below $500 a share after the burrito chain reported revenue slightly below expectations in April and said the removal of pork from one-third of its restaurants would hurt sales this year, Barron’s said. Rising food costs, along with rising healthcare and other costs, are crimping Chipotle, it said.