The retail pharmacy giant faces ever-mounting headwinds.Shares of Walgreens Boots Alliance (WBA -3.57%) plunged 22.1% in August, according to data from S&P Global Market Intelligence.The beleaguered drug store chain didn't even report earnings last month and was already out of favor heading into August. But Walgreens saw incremental headwinds, especially the news that more drug companies would be introducing direct-to-consumer offerings.Is Walgreens getting disrupted by DTC?Walgreens has been under fire all ...