Septoria Leaf Spot is one of our most common tomato diseases, and it's not unusual to have repeat infections in home gardens. Spores can be windborne and years with wet weather can favor higher infection rates. The usual precautions apply to reduce the risk of heavier outbreaks -- remove the lowest leaves on tomato plants as they mature (as they tend to be infected first, giving the spores a "ladder" to splash higher up into the canopy), water plants in such a way that foliage stays dry or can air-dry by nightfall, and clean-up all plant debris (dead leaves and stems) at the end of the growing or harvest season, so they don't harbor spores. You're already taking at least some of these steps, though soil replacement is not necessary and won't affect much, since spores can move on the wind. Some tomato cultivars may have more resistance to Septoria than others, so this plus the weather will influence how abundant or not the disease is from year to year. Copper sprays, used as directed so it's not over-applied, are a suitable approach at this point to discourage further infection.

Miri