#23 Unknown, though the death chants, the return of surgebinding, and a bunch of other stuff all started happening around the same time the Parshendi showed up. Or maybe it was closer to Gavilar's assasination. There may be a cause and effect there, or those may just be more effects of some other cause.
#24 Probably something to do with the Stone Shamans. They might have been able to protect information better since they don't need to worry about highstorms.