There are spores and bacteria aplenty in the soil and air, but no test i know of outside of a lab. You'll find the treatment (prevention of worsening, really) is the same for most foliar diseases...spray regularly with a copper based or chemical spray. Chlorothalonil is the active ingredient most commonly recommended. Removing the damaged leaves and fiscarding them is also on the to-do list. Get at it ASAP...most problems can be managed, but they can overwhelm your plant if you don't treat. (I've done the wait and see route, and I don't recommend it! :)

There are also many websites that have photos and discriptions of common problems for you to match yours to. That is how most of us diagnose our plant ailments. Posting photos here will also help.

I looked at so many photos that I got dizzy! It sort of looks like salt damage to my untrained eye. I have raised beds. I dug down about 12 inches before I build them, and the beds are about 12 inches.
The camera is not here now, so I tried to use an iPad to take the photo, and then email it to myself. I can get a better photo later.