Naw.
And the issues with stairs... that famous picture with her "tripping" on the stairs (actually being all but carried up) is not the only picture of her having difficulty with stairs. There are several pics of her being supported on stairs, and even when just standing.
Maybe the media is trying to cover up her health the way they did with FDR, but these days, with the open internet and massive social connectivity, it is really hard. So the media has to resort to claims of conspiracy, telling us that we are imagining signs of poor health when we see it.
What is the real reason she is not campaigning?
Her coughing is probably due to severe GERD.
GERD Symptoms List: Cough, Chest Pain, Nausea, Sore Throat, and ...
www.webmd.com/heartburn-gerd/guide/understanding-gerd-symptoms
WebMD
Mar 3, 2015 - If acid reflux gets past the upper esophageal sphincter, it can enter the throat (pharynx) and even the voice box (larynx), causing hoarseness or sore throat. Chronic dry cough, especially at night. GERD is a common cause of unexplained coughing. It is not clear how cough is caused or aggravated by GERD.