With the major indices continuing to set fresh records, it can be tough for investors to feel comfortable buying into names already trading at highs. However, at the other end of the spectrum, it can be just as tough to buy into a stock that has been sinking like a stone—or, as Wall Street likes to say, to catch a falling knife. Currently, two stocks firmly in that camp are The Trade Desk Inc. NASDAQ: TTD and Duolingo Inc. NASDAQ: DUOL, which have shed close to half their value this summer. Both have been i ...