One of the signs that a stock has risen too far, too fast and is, therefore, in need of a breather, is when it closes above Resistance at an Upper Bollinger Band.
The QQQQ closed above both its Daily and Weekly Bollinger Bands on Thursday, not to mention the upper end of its '10-Week Trading Band'. That doesn't necessarily mean that the rally is over. It does mean, however, that the QQQQ is overdue for a rest.