“Follow the money” is good advice in investing, but following the smart money is even better. The mortgage and related services industry group is riding high. The group was No. 17 of 197 groups, as of Friday’s IBD, but that’s down from No. 2 six weeks ago. Should that slippage matter? Some fluctuation in the ratings is normal. While slippage isn’t a deal-breaker, it calls for a closer look.