Alternaria leafspot (on crucifers)
Cabbage black rot
Cabbage soft rot
Celery early blight
Celery late blight
Cucumber downy mildew
Plants begin to degrade the chlorophyll in the old ( lower ) leaves, giving the leaves a marbled appearance.
Symptoms include poor plant growth, and leaves that are pale green or yellow because they are unable to make sufficient chlorophyll.
Brown scorching and curling of leaf tips as well as yellowing between leaf veins. Purple spots may also appear on the leaf undersides.