DOW AND NASDAQ FOLLOW S&P DOWN

The Dow, (here echoed in the DIA ETF on the DOW 100 shown green), quickly followed the S&P, (here echoed in the SPV ETF on the S&P 500, shown blue), and then the NASDAQ (here echoed in the QQQ ETF on the NASDAQ, shown blue), joined in the dip. It is too soon to say if this is the beginning of a downtrend, but why not, since the indexes are overvalued?