I hate to say it, HashGirl- but unless they get some additional nitrogen, they may not green up at all...
2 of my plants did the same thing...one of them got additional nitrogen in the form of Calmag- (8-0-0) all it's life, and it didn't green up till a week before harvest- and that one was fed GF Veg exclusively, which has considerably more N than GF Bloom nutes...
If yours are yellow now, on veg nutes, it's just going to get worse when you make the switch to bloom nutes.
My second yellow plant was ok till I switched to bloom nutes- then, within a week, it also started yellowing...I finally said to hell with it, and switched back to my old nutes- within 6 days, it was green again...
If you or Felonius have anything in your nute stash with a decent amount of of nitrogen in it, you might try giving your plants a dose of it to see what happens- it isn't going to hurt them, because they're definitely hurting for nitrogen right now...
Just don't give them too much- even though they need nitrogen, giving them too much too fast could still burn them...just kind of ease them into the extra nitrogen, allowing a week or so between applications...
I know you didn't ask for suggestions, but I figured I'd throw one out there anyway...
I hope that's ok...