Former HHS chiefs to Trump: Stop undermining Obamacare
President Donald Trump (Twitter)

WASHINGTON - Don't make things worse. That's the advice of former U.S. health secretaries of both parties to President Trump and the GOP-led Congress, now that "Obamacare" seems here for the foreseeable future. The 2018 sign-up season for subsidized private health plans starts Nov. 1, with about 10 million people currently served through HealthCare.gov and its…