If your purchasing plants from a reputable nursery or garden center, they should be able to inform you about the health of the plants they are selling.
Plants can appear healthy at purchase but become susceptible to the air born fungus downy mildew.
Many growers are producing impatient varieties that are resistant to disease. If you love the plant it may be worth searching out these varieties.
If your unsure of the health of the plants I would choose another shade loving annual to enjoy.