By 1928 did some economists start to issue warnings about the health of the economy and the stock market?

Yes, by 1928, some economists began issuing warnings about the health of the economy and the Stock Market. They expressed concerns over speculative investments, excessive stock market speculation, and the growing disparity between stock prices and actual economic fundamentals. These warnings foreshadowed the impending stock market crash of 1929, which ultimately led to the Great Depression.