Woohoo, that's a big change. Did you have a compelling form/anatomical/fit reason for doing this? One CM is a mile when it comes to saddle height; I usually tell people to adjust no more than 6mm per ride in any direction, unless they know, for some reason, that they're grossly off. If you've dropped it too low, your thighs will absolutely burn because your position is bad. In fact, a saddle that's too low can sap 15-20% of your power, at a minimum.