I sure wouldn't give it any supplements since you may over do it on one end and cause a problem in another. That Foliage Pro had plenty of iron and god forbid once your tree starts to take that nutrient up with the iron in the ground already..

Why don't we try and figure out what the source of your issue is?

How have the temps been? Where do you live? That is for starters...

Do you or have you ever used vinegar or had your tap water tested?

What kind of mix do you use? Homemade? Bagged?

Just a bit of info for you about using too much Iron which your fertilizer has plenty of. Something is preventing your tree from taking it up...

Iron is considered a micro-nutrient because only ...small.... amounts are required to aid in normal plant growth. It plays an important role in respiration, photosynthesis and the production of healthy green leaves. Plants can suffer iron deficiency with symptoms of chlorosis and stunted growth, but plants can also take in too much iron, especially under certain growing conditions.

Iron and Plants

Iron is mainly involved in the process of plant photosynthesis. The micronutrient's availability to plant roots depends on the pH level of the soil with iron more readily available in soil with a low pH. Iron and manganese both play an important role in plant growth and development, but often compete for absorption, as an abundance of one of these micronutrients makes the other less available to plant roots. Fertilizers should contain an equal ratio of manganese and iron so both are readily available to plants. This is what your Foliage Pro already does for you.

Iron Toxicity

Iron toxicity is not common, but some plants do secrete acids from the roots, which lowers soil pH. These plants can take up too much iron, leading to toxicity. The symptoms of iron toxicity include bronzing and stippling of leaves. The leaf discoloration is caused by the plant creating enzymes to control free radicals that are present in high iron levels. Some plants that are prone to iron toxicity include tomatoes, basil, phlox and impatiens.

Iron and Manganese

High iron levels often cause manganese deficiency in a plant first, because of the two micronutrients' competitive behavior. Manganese deficiency exhibits similar symptoms as iron deficiency, such as yellowing of leaves, except manganese deficiency affects both young and old foliage, while iron deficiency affects only young foliage. Iron and manganese toxicity have similar symptoms in plants as well.

Causes of Iron Toxicity and Prevention

Iron toxicity also can occur when chelated iron is added to soil. Chelates help increase nutrient uptake and solubility of metal micronutrients, which in turn makes over-absorption possible. To avoid iron toxicity, check pH balance and maintain a pH level of 5.8 or higher when growing plants prone to iron toxicity; use a fertilizer with a balanced ratio of manganese and iron; and use iron chelate, like Foliage Pro.

So as you can see, it's not just the YOUNG foliage with issues but the whole plant. Then too, you can over due it on the Iron side causing worst issues..