Certified GKH Gardening Expert
This could definitely signal too much water and the cause of your leaf yellowing. While there's little you can do about the rain or cooler temps, just make sure not to water them until after they have dried out some. Once the raine has ceased and the ground has dried, the plants should eventually recover on their own.
an old farmer said it was not fungus like st augustine but a lack of ca+ and to treat it with evaporated milk. it did not work on the two of my varyities of tomatoes. just thought i would mention it.