I have always maintained the grand jury was not looking into who leaked Plame's name (primarily) and once that issue was set aside they had other issues.
My guess is these reporters were recipient of illegal leaks from a rogue or rogues at the CIA and/or State to do with intelligence.
BTW, don't forget Fitzgerald has another grand jury (it's reported as a separate grand jury) that also wants Judy Miller to testify.
That's the one looking into someone tipping off her and her colleague Philip Shenon that some Islamic charities were about to be raided.
Fitzgerald has stated flatly in his subpoena that they have discovered for a fact that Shenon received the information and told the charity on the eve of the raid and that this tip resulted in evidence being destroyed.
You really, really got to read this.
http://www.nytimes.com/2005/04/22/nyregion/22bold.html