The stock market sell-off in recent days has tripped a number of warning signals that point to more pain ahead for investors. The tech sell-off stretched into a fourth session on Tuesday, declining on a cocktail of worries while the market also flashes several red flags for investors to be wary of. The S&P 500 crossed a key technical level that could hint at more weakness to come. The benchmark index dropped below its 50-day moving average on Tuesday — the first time it's done so over the last