There are no raised bumps underneath! Leaves were fIne until the end of summer!
Is It Ok to Eat Basil Leaves Spotted With Rust?
Unless you know for sure what the infectious agent is, I wouldn't eat the leaves. And of course, certainly don't eat if you've sprayed with a chemicals. This article on basil diseases may be useful to you: https://www.gardeningknowhow.com/edible/herbs/basil/basil-diseases.htm