Volume on QQQ advance today was 17m shares, c/w 41m on 20 June. Eking out marginal new highs on vanishingly smaller volume, 1/3 of the previous high.
SPY traded 61.5m shares today but on 20 June at the previous ATH it rose on 116.5m shares; volume is half on this lift.
Dow Theory: Volume MUST confirm the trend and Divergences in averages (DJT, RUT) occur near change in Trend.