I just heard about this yesterday..... check out the article on the Trochanter Mealybug.  I had never heard of it before....

with your crop history, I could expect K2) deficiency.  However, it might pay to take a tissue test to see what is in the plant; and to get a shovel out and start digging.....  

P.S.  if you find the mealybug, let us know - it would be interesting to know how prevalent it is.