Maple with split personality.
Half of the maple outside my NW DC condo is turning now. It will be bright red before the other half turns. A stark split. At least the second year like this. A few branch ends on the early half have been leafless all summer. Otherwise, both halves seem healthy. Do I have a problem? Your insight earnestly sought.
The roots under the side of the maple with the "early fall coloration" have a problem. They are not supplying water and nutrients as needed. The portion above those roots are responding by calling it quits early in the growing season. This is not good.
We can't say why it's happening. If you send a photo of the whole tree, we may be able to spot something in the environment, but rarely can anything be done to correct root issues.