That looks like a typical badly starved tomato plant.
Now the reason why that happened, is hard to tell, but I can't imagine the soil is so extremely poor. Something is stopping root uptake of nutrients, either way too much water for longer periods, or wrong pH, or something eating the roots. In any case, it is not a fungal disease, aged leaves that turn yellow due to lack of nitrogen are sensitive to anything fungal, they will just rot (it might be some sort of virus, but I'm no expert in those, doesn't look like the usual suspects).
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