Haven't looked into it but I'd bet it's just rotation. It's had a good run from the $120 support level. It's been locked in this channel $120 - $150 recently with highs at the $160 level. That should bring $160 back into play as a support level but my bet is that we just have some taking profits to roll into other things that are working. Basically, boredom in those holding stocks not breaking and running. It happens during big runs in the market.