Amur maple leaves changing color

Hello,

I have 3 Amur maples and this is my first autumn with them.

I believed they were all the "flame" variety, but one of them in particular has started changing color a lot earlier than the other two. The leaves have quickly changed to a yellow color and some are becoming red in areas, but I was concerned it was perhaps a bit early for this and was wondering if the overall yellowing could be caused by something else. It was my most healthy looking one throughout the summer. The yellowing has been accompanied by small black spotting on the leaves. It doesn't look like regular fungus I saw on my other tree. Could it be suffering from lack or iron, or is turning yellow before red normal?

Thanks

Chill. It's time for them to change. Each tree is a little different. The black spots are probably tar spot, a common maple fungus. Clean up fallen leaves & dispose of them. You could use a dormant spray this winter to control the spores. If it is rainy next spring, use a preventive fungicide that is listed for maples.
Iris

I second that.

I have Amur maples too, and they're the ones that are the more prone to chlorosis and fungal diseases among all the maple species I have. I'm afraid that my "environment" (water, temps, etc) are not the best for Acer ginnala.