Not sure what is happening to tomato plant

Looks like too much water, or a deficiency..try some chelated iron and/or some epsom salt magnesium sulfate even a "miracle grow type" fertilizer can help the issue some, but will take more applications to get the results you want but i wouldn't do so until next water cycle, or in the heat of the day..a good indicator of when to water tomatoes is when they ever so slightly start to wilt, or just buy a moisture meter and check it every day.. they can be sensitive to over watering and even rain can cause that

The structure looks good, maybe the roots have remained too wet from the rain: even if theres 2 or 3 cm of gravel under the soil for drainage & aereation, the soil many have compacted around it from the rain resulting in inadequate drainage & aereation. And if applying a granular type of nutrient, there might be excessive nutrient dissolved too rapidly by all the rain and overwhelming it.

If its waterlogged roots, then alleviating that could help!