The debate over masks is heating up again, with increasing calls for all Americans, regardless of coronavirus vaccination status, to return to wearing face coverings in indoor public places to help thwart the spread of the highly contagious delta variant. But some experts say the recommendations should specify the kind of masks people should be using. Support our journalism. Subscribe today. “Delta is so contagious that when we talk about masks, I don’t think we should just talk about masks,” Scott Gottlieb, former commissioner of the Food and Drug Administration, said during a recent appearance on CBS’s “Face the Nation.”...