My tomatoes get spots and die back every year
Most of what gets called blight is soil-borne and arrives by splash. Three free changes to how you water and mulch do more than any spray you can buy.
What actually works
The spores overwinter in the soil and get onto the lowest leaves when rain or irrigation splashes. A mulch layer physically stops that, and it is the single most effective thing on this list.
Drip or a soaker, in the morning. Wet foliage overnight is the condition every one of these diseases needs.
Those leaves contribute little and they are the landing zone. Space plants for airflow while you're at it.
Tomato, potato, pepper and eggplant share the diseases. A bed that grew tomatoes shouldn't grow any of them next year.
Look for the letter codes on the packet. It's free to choose better.
Milk has some real but weak evidence against **powdery mildew** specifically, and essentially none against blight. These circulate as cures for everything, and they are not.
Also searched as
tomato blight · early blight · late blight · septoria leaf spot · yellow leaves tomatoes · tomato disease · leaves spotting brown