The purple and curled leaves look like a deficiency in the soil or possibly exposure to drifting herbicide. The brown is more along the lines of something infectious a blight or some type. The yellowing with spots looks like Septoria leaf spot. Those are all somewhat treatable.
I am worried about the quick rise in your pictures of yellowing leaves and maybe stems too - can't tell bc picture is shot with the golden bath of evening sun. If you are getting a lot of yellowing leaves and stems moving quickly up the plants, that could be Fusarium and that is a much bigger problem because it is in the soil, not treatable and you will have that problem year after year. There is a test you can do involving looking at the inside of the stems. If they are dark colored inside, you have it. If you have it, you'll either want to rotate out to crops not susceptible for 3-5 years or plant tomatoes with fusarium resistance. Some folks here use grafting on root stock that is F resistant with success. Good luck.
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