The picture on the left is a close-up of the maple at the end of my driveway, the one on the right is a platanoides drummondii.

Everyone on my street has the same tree, only theirs are more mature (my neighbour's and mine was replaced a few years back). The problem is that up until this spring, all of our leaves were dark green. Suddenly, they look like this. The more mature trees are half dark & half variegated-looking. When the leaves first came in, they were a bright green (like the centre part), and then changed into this colour, and have remained this way since.

I just want to make sure it isn't some kind of disease, or malnutrition, as I would want to try to save it. Thanks in advance.