Does it start at the bottom of the plant and work its way up ? If that's the case then its most likely a nitrogen deficiency and the yellowing is her eating her leaves for nutrients we want this to happen in the flush but not in early or late flower but if you give her one dose of your vegetative nutrients that should give her enough to finish up :) she's a large plant to strip of nutrients so the fact she is showing these signs is kind of a good thing. Just up her feed and you'll be fine I know its hard to not overfeed but over feed symptoms are brown edges that go inward :) and it appears very rapidly and is very easy to spot :)