Hi again CK, I went asking around looking for an answer to feeding a seeded plant and the advice seems to be normal balanced Veg nutes right through the seeds ripening. Here's a quote from an old school grower: "I should say a well balanced nutrient, don’t skimp out on the N. Gives them more of the nutrients that’s needed for seeds, and hopefully Keeps them from fading out before the seeds are mature. I’ve been giving the seeds 6wks from the last pollination, or until the buds themselves die and dry on their own and the seeds are popping out."
I kept on the normal flower nute schedule and still got a good result but his advice is probably better.