Recent comments made by two of Nvidia's biggest customers could be viewed as yellow flags.In the late 19th century, coal miners began bringing canaries when they descended into the mines. If the canary became distressed or died, it was an early warning sign that dangerous levels of carbon monoxide were present. Investors today don't have anything as simple to use in detecting problems for companies as canaries in the coal mine. However, paying close attention to comments made in the quarterly earnings calls ...