Mayor Bill de Blasio says that “universal health care” is one of the local issues he’ll focus on now that he’s given up on his White House run. He’s got his work cut out for him. The latest Mayor’s Management Report shows enrollment in MetroPlus, the city’s health plan for low-income people on Medicaid and Medicare, fell 3,000 members to 519,000 in the latest fiscal year. Yet, according to NYC Health + Hospitals, applications are up 15 percent.