Wow, you came up with a tomato disease I had never heard of! I looked it up and it is caused by a phytophthora fungus, which is the same genus that includes the root rot fungus.
Lindsay was spot on: "The first symptom on the fruit is a grayish green or brown watersoaked spot that develops where the fruit touches the soil." https://pubs.ext.vt.edu/450/450-704/450-704.html
So it sounds like the same preventative measures that we generally suggest to avoid tomato fungal diseases apply here: keep the tomatoes staked or caged off the ground, remove the leaves at the bottom so that nothing is touching the ground, mulch heavily to help keep soil from splashing up and only water the soil, not the leaves.