Gee WaPo does a article about this. Must be a huge issue if they are trying to put a lid on it.
Remember, I believe she's scheduled to be at a fundraiser being held by Apple CEO Tim Cook on August 24, 2016. Given that Cook knows what it's like to deal with a close friend in declining health in Steve Jobs, the Clinton campaign better put a lid on these rumors or even Tim Cook is going to start asking questions in private about Hillary's personal health.