I start all my vegetables in my house from seed germinated under a grow light. For the last three years my tomato plants have been devastated by early blight / septoria but I keep trying. I start spraying with Fungonil / Chlorothalonil as soon as the plants are put outside to no avail. This year I noticed a discoloration on the stem of one of my Bush Early Girl tomatoes that I have not encountered before. There are no symptoms anywhere else on the plant. I am hoping that is not the beginning of a fungus. Normally the fungus starts on the leaves and eventually murders the plant in June. I planted these tomato seedlings on May 6 in five gallon containers. They all look fine with no other issues except the the one with the stem discoloration. I would appreciate opinions on what the discoloration shown in the attached images might be? Thanks.