as you cut down on nitrogen in flowering, the fan leaves yellow, die and fall off, this is a good thing...you don't need alot of Nitro in bloom, and you want the plant to use it up.
this will allow plant to process all the nitrogen; dry and cure faster, and taste better...also, you have a somewhat weak solution for wk4f, but that's OK...you won't nutelock them that way.

If your overall plant looks OK and all that is yellowing are larger fan leaves, then:thumbsup: Don't worry.lw