Nasdaq 100 futures are leading the early declines on Tuesday. That's perhaps not surprising given how much the tech-heavy index has rallied. Using the Invesco QQQ Trust Series I as a

proxy, the exchange traded fund, known in the market as the Q's and which contains the likes of Nvidia and Microsoft, has jumped 25% since its trough on April 8. That swift advance has

left the Q's 14-day relative strength index, a momentum gauge, at 71.85, the highest since last July, according to Dow Jones data.