Answer: It cound be that vertilcilium wilt has settled into your garden. Once it gets into the soil it can last for years. Cut the stem of the tomato to see if it is discolored to brown inside. If so them wilt is the culprit. Growing new plants or seeds that are verticillium and fusarium wilt resistant in new raised beds or containers with new clean soil for a few years is one solution. You should make sure that all old vegetation has been cleared and burned. The other possibility is early blight, but the copper should have controlled that as long as you sprayed early enough in the season. I'd say try some new varieties such as 'Celebrity' and 'Big Beef' with added wilt resistance.
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