Assuming it is leaf septoria, you can try cutting out infected leaves and using baking soda ( add a heaping tablespoon of soda, a teaspoon of vegetable oil, and a small amount of mild soap to a gallon of water) to spray on plants. This needs to be reapplied regularly to maintain its efficiency.
Having said that it has been a difficult year here (eastern Ontario) for plants, I harvested much earlier than usual because of the really high humidity levels we have had since start of August it seems. Right now it is raining, 100% humidity and 0 wind and it has been like this for what seems months, not a lot of sunshine here either for the past two months, but warm and humid and no wind, so yeah, lots of mould like problems this year.