Basketball great Julius Erving — Orlando Magic executive vice-president Dr. J — asked his fans on national television yesterday to help find his troubled 19-year-old son, Cory Marvin Erving, who was last seen on May 28. Erving posted a $25,000 reward for the teen’s safe return. This morning, an investigating sheriff said during a “Today” show interview that Cory, who was officially declared “missing and endangered,” might have had a drug relapse and might be using crack cocaine. Seminole County (Fla.) Sheriff Donald Eslinger said that his department is investigating a confrontation that Cory reputedly had in a well-known drug-dealing area shortly before he was reported missing. In his news conference Tuesday, Dr. J said that Cory “was born with a learning disability” and has had a drug problem for the past five years. This morning, Eslinger said that more than 100 calls have been received on special search hotline for Cory, and that his department is following up on them.