| Tomato blight is a difficult disease to deal with. You'd better uproot your plants and plant others far from the infected soil. Try not to overwater your soil for fear of spreading the fungus all over. Alternatively you could disinfect the soil with a soil fungicide, letting your plants where they are.If you do so, take care the fungicide doesn't last more than 1 month if your plants are small, so as there will pass some time until they bear tomatos. But if I were you I would plant others to a different spot. Good luck | 
