Iron Chlorosis can be a common problem for some species of oaks. It can be caused by a lack of iron or manganese, both key elements in the chlorophyll molecule that provides the green color. this can be seen visually by the veins being dark green and tissue between the veins a light green or pale yellow. It can become worse over time. If this is occurring and the cause is an iron deficiency, treatments are warranted. this can be caused by a lack of iron/manganese in the soil or a soil pH that ties up the elements. A soil test would reveal the pH level. Tissue analysis would show if it is iron or manganese. Proper diagnosis is key for an effective treatment and recovery