It is true that some nitrogen is needed up through the chop, just don't be feeding your ladies nitrogen like you would in veg. It is also true that your colas should not have leaf yellow. Just go easy peasy on the N.
this is what I was saying, a 3-4-3 or something silimar is usually enough nitrogen, in your case, it may be something different than a nitrogen issue (judging by the odd color)
A worm casting tea, or even a rabbit manure tea would be a great LIGHT nitrogen feed...
I wouldn't use any nitrogen heavy foods though, a LIGHT sprinkling of seabird guano would be good too, but like I said, if you have reddish colors or "rust" color it's most likely NOT a nitrogen issue.
But no matter what, I feed my plants teas that have nitrogen up until the last 10 days, then I let it just suck up good clean water.
you just don't want mass amounts of nitrogen in the flowering phase because it can lead to "leafier" buds, not to mention some strains get "confused" when fed a lot of nitrogen during flowering, which leads to irregular bud formation.... not to mention a shitty smoke