From the story here:
FBI policy forbids any agent from releasing classified information or any information from ongoing investigations or sensitive operations without prior written permission, and mandates that all records created during official duties are considered to be government property. ...
[T]he revelation that four of the seven memos included some sort of classified information opens a new door of inquiry into whether classified information was mishandled, improperly stored or improperly shared.
Ironically, that was the same issue the FBI investigated in 2015-16 under Comey about Clinton’s private email server, where as secretary of State she and top aides moved classified information through insecure channels.