With a Zinc Deficiency, the signs always appear on the new growth of the plant and turn the leaves a lime green color. Pretty early on, growth begins to slow down and can even completely stop. If the problem is not corrected, the leaves will eventually die off completely.
How to Cure:
Just like with a Potassium Deficiency, this issue is usually caused by incorrect pH levels in nutrient feedings. Always be sure to check your are using the correct pH before changing anything else. Once that has been confirmed, you want to check that the conditions in your grow space are optimal as a Zinc Deficiency can be caused by a stressful environment. Other than that, the only other cause would be from a lack of nutrients in the growing medium. So be sure you are using a soil or additive that contains Zinc!