I bought Marvell also from NDX100 which actually have same as MSFT as far as I can see it does but a bit different way.
I think there is cute conflict going on while with Dow, SPX and NDX.
If you are indextrader with SPX you have very difficult times ahead because some of the stocks are ultra bullish while some are not as earlier mentioned this behaviour. Dow might become the weakest Index while NDX as strongest one. SPX something between.
It´s picky environment.