Ask-a-Dave's-Gardener: Why is the new growth on zucchini plants yellow?, 1 by Zen_Man

Zen_Man wrote:
So you have established that the nutrient deficiency is not Magnesium or Sulfur. I suggest you apply a complete soluble nutrient formula. As far as I know Miracle-Gro does not have a Zucchini Food product, but they do have Miracale-Gro Tomato Food and I recommend that you apply it as a foliar feed according to the directions on the label. I apply it to my zinnias as a drench with about one tablespoon of product dissolved in a gallon of water. It comes with a little plastic spoon sized for a standard watering can.

ZM (not associated with Miracle-Gro)