July was a quiet month but August started with a bang.Shares of app-based education company Duolingo (DUOL 13.59%) dropped 17.6% during July, according to data provided by S&P Global Market Intelligence. Without any news to excite investors, the stock drifted lower throughout the month. But that's already changing in August with the release of its latest quarterly earnings report.The S&P 500 was up 1% during July so it may be surprising to some that this was its worst July in a decade. In short, market cond ...