Plants move nutrients to where they are needed most. Since a plant will try to supply more nutrients to younger leaves rather than to older leaves, symptoms of a nutrient deficiency will appear first on older leaves. However, not all nutrients are equally mobile. Nitrogen, phosphorus and potassium are mobile nutrients while other nutrients have varying degrees of mobility. When a less mobile nutrient is deficient, younger leaves suffer because the nutrient does not move to them and stays in the older leaves.
Early diagnosis of nutrient deficiency in newly emerged leaves can be corrected with a soil or foliar application of Stoller fertilizer and micronutrient products containing the deficient nutrients.