wrong forum! I didnt know there is a tomato pests and diseases forum .. Anyway, I found a similar situation discussed here .. older thread
One of the suggestions is that water on the leaves with bright sun .. I did spray water on that plant in the afternoon, assuming the trees would like the "rain feel". Of course when it rains, sun is not bright .. so this probably never happens during regular rain.
Can that be the explanation for this necrosis? And in that case, it should recover fine, right?

I don't buy the idea that sun on water droplets on the leaves will harm them in any way. That happens too often in nature for us to have no evidence of it in the wild. What I see on your plants doesn't look like a disease or malnutrition to me either. It is some kind of stress, possibly sunburn or insect damage. Sorry I don't have a more specific diagnosis.