Another sickly water oak

My neighbor behind me to my east has a dual trunk water oak that’s shedding leaves right now like it’s fall. We’ve been here since 08 and have never seen it do this.

A little back story…we put in a pool and pool house the last couple yrs. We had to remove a live oak for our project. The arborist looked at the neighbor’s water oak and didn’t give it a clean bill of health. The neighbor is an older, divorced lady and has a pool as well. So I offered to pay for the tree removal and they were going to take it from my side of the fence. They’d only need to go in her yard to grind the stump. She declined due to the afternoon shade it provides her. I have a feeling that decision is going to come back and bite us both in the butt.

Any idea what’s going on with the tree? The leaves look like some kind of fungus to me.