The ProShares UltraPro QQQ ETF (TQQQ) closed on January 27th at $79.14, down 8.77%, as the Nasdaq 100 faced a significant selloff, driven by concerns over a new AI model from Chinese startup DeepSeek. This model, developed at a fraction of the cost of U.S. counterparts, has raised doubts about the sustainability of high valuations for major tech companies like Nvidia, Microsoft, and Alphabet, which are heavily weighted in the Nasdaq 100. Nvidia, in particular, saw its stock plummet nearly 17%, erasing substantial market value and highlighting the vulnerability of tech stocks to competitive pressures. The broader market sentiment was further dampened by expectations of slowing earnings growth for key tech players, adding to the risk-off environment.