By Stephen Culp NEW YORK (Reuters) – Wall Street turned lower on Wednesday as a string of corporate earnings ran the gamut from downbeat to dismal, reviving worries over an economic downturn. All three major U.S. stock indexes were red, but off session lows. The tech-laden Nasdaq was down the most after Microsoft Corp, the first major technology firm to post quarterly results, offered dour guidance and raised red flags with respect to its megacap peers which have yet to report. “The slowdown in the economy and in the labor market is starting to materialize,” said Oliver Pursche, senior vice pr…