New Jersey online gaming brought in 15 percent more from online gambling in March over the previous month, but it wasn’t nearly enough to offset the diminishing revenue from Atlantic City’s long-struggling brick-and-mortar casinos. The state Division of Gaming Enforcement reported Monday on casinos’ gambling winnings in the latest edition of a monthly report where the news has been mostly discouraging for years. Online gambling, which was launched in November as the latest hope to reverse Atlantic City’s fortunes, hasn’t brought in the revenue that was expected. But it has grown each month. In March, the casinos won $11.9 million…