CPU usage very low during concurrent large updates

Hello,
We have two updates running concurrently one of which is running an update of a couple million rows. It usually takes a few minutes, but took about a half hour. I was looking at the CPU activity and using sp_who2 throughout the process. The CPU was hovering around 3-7% for awhile. It seems to be hovering around 40-50% for the next update which again is taking longer than normal. When using sp_who2 the two updates seem to spend the majority of their time "sleeping" instead of "runnable". It seems like SQL Server isn't using as many resources as it could, mainly CPU, also it seems one of the updates should be "runnable" in sp_who2. Any opinions would be appreciated. Let me know if any more info is needed.
Thanks,
Gunner

No, but I did run DBREINDEX to improve the scan density, which was pretty bad. Probably less than 40% on all five indexes.

Same performance issues. It looks like my problems are related to changing a decimal(9,2) to decimal(14,2). I changed them back to (9,2) and I'm getting closer to normal performance. I see a precision of 9 is the cutoff for 4 byte storage tier and 14 would be 9 bytes.