baggersup,
The CSD or SCCM does set the tone of a crew very much so.
On you flight out of IAD it could have been the last sector of a back to back trip. These are trips where the crew do 4 sectors back and forth to the States in 5 or 6 days, not going home when they get to LHR in the middle of the trip. It is no excuse but likely why they may have lacked luster.
Hopefully you will get a good CSD next time and more likely, if you fly on a strike day because a lot of the best keen ones came in to work.