i dont know exactly if is zink defiency. can fix problem with amino acids?
mate, excellent paper... a must read for every grower!!better think about a general nutrient imbalance first ... before you go isolating the problem down to an individual mineral like Zinc.
to see what I mean look at the chart on page three here:
http://www.nutri-tech.com.au/downloads/Hydroponic Program.pdf
(that should read "...downloads/Hydroponic%20Program.pdf)