Thank you. There are a number of different blights and diseases that can affect tomato plants. I think mulch helps in my garden because some diseases can be splashed up from the ground when it rains. Others diseases/blights are caused by spores in the air. Try not to let the leaves get wet when you water and try to water in the morning. Also make sure you have good air circulation for your plants. If the bottom leaves turn brown or spotted break them off right away before it spreads. Good luck.