What is blight in tomatoes?
Blight
a rapid and complete chlorosis, browning, then death of plant tissues such as leaves, branches, twigs, or floral organs
Blight is a rapid and complete chlorosis, browning, then death of plant tissues such as leaves, branches, twigs, or floral organs.[1]  Accordingly, many diseases that primarily exhibit this symptom are called blights. Several notable examples are: