Answer: Based on your description it is difficult to give a definite diagnosis but it is possible that the plants are suffering from verticillium wilt. In older plantings, the symptoms of this fungus appear as the fruit begins to ripen. The older outer leaves wilt and turn brown around the edges and between the veins, and this can give the appearance of yellowing on some leaves. You may also notice the leaf petioles turning red and/or the crown and roots turning brown.
Although this particular planting seemed healthy, it is possible to spread the fungus from one bed to another on your tools. Unfortunately, the best way to control the problem is to plant only resistant varieties from now on.
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