Basil doesn't get early blight. Have you checked for Downy Mildew?

Mine look like that, only worse. I don't think its downey mildew, but possible since my zucchini has some white spots on the leaves. Should I spray the basil with a mix of baking soda and water?

It's definitely Basil Downy Mildew. It won't affect other plants. Don't over water and make sure it gets air circulation. You can try using a copper fungicide (that's what I tried) and see if you can stop it. Won't cure it but could help.