Looks like insect damage to me, I can see from what is growing around the maples, (hostas, spider plants etc) that this is a shady area, and trees that require full sun, such as maples, will grow very soft leaves in shady situations, leaving them prone to insect attack.
Leaf miners at work by the look of it.
If the rain was toxic, it would effect everything, not just a few leaves on a couple of plants.
Just another person looking for youtube fame, and getting on the Gulf victim bandwagon.