Each preferred share prospectus would need to be altered individually, so it's not a gang-vote of all pref holders, but rather a per-security vote.
Another way, 66.6% of FMCKJ holders would need to vote in favor of whatever the proposed adjustment was. Regardless of which way it went, that vote can have no impact on the holders/prospectus of FNMAS.
Sr. prefs get NO rights in this. The prospectus and its language applies only to the series it covers.