I would mix that soil with very old horsemanure, lime, mulch, hay, grass & leaves and turn it in. PH for tomatoes is 5.5-7.5
If blight happens again, take the whole plant out and bag & trash it........wash your hands as you don't want to spread it around the garden. This happened to us one summer when we had so much rain. I removed the green tomatoes pulled out all the effected plants and bagged & trashed them. Please do not mulch these as you will keep the blight in your garden.