add 1/3-1/2 strength grow formula(nitrogen) and the same amount calcium/magnesium/ and if you can get your hand son kelp add a lot of that. a full dose.
not too much nitrogen it's easy to overdo. you'll get the tops way to dark and over nitrogen and the bottom still will stay yellow.
You have to be patient ... give the feeding i just said 2 feedings in a row ...
my advice is good, if you have all 3 of those, greg, if not, id get what you're missing
in the future, give a good 1/3-1/2 strength Grow formula the first feeding of flower ... after stretch is out, or rather the last 2 weeks of a 4 weeks stretch you switch to flower formula. They like N up and through the stretch and into first week of tossing out pistils
pH too high! but your plants may have finished their growing and so the leaf yellowing is normal (the sugars from the leaves translocate to the heads) for a finished/nearly finished plant.