I've had this problem too. I think it is because they made a lot of their rooms "allergy free" and added special filters (so higher room category). That's what they explained to me a few weeks back at least.
One of my favorite hotels in the US. Going back to DC Oct 1-3 and checked online for a reservation. Rates for the weekend are 700 per night! Never even paid half that. Anyone know what's going on? Rates at other hotels seem normal for this time of year while the PH seems off the charts.