Blights are common problems on tomatoes.
Healthy plants are the best defense
Use a drip watering system or water at the base of the plants and avoid wetting the leaves as much as possible
Wet humid conditions encourage fungal issues. If you cannot control the environment, use preventive anti fungal sprays when humid conditions are present
Space the plants well, crowding limits air circulation and encourages fungal issues
Mulch is a good thing, so is removing the lower leaves.
If you have had problems with fungal disease before, good sanitation is a requirement. Pull diseased plants so they don't spread the spores, burn the debris and make sure your hands, clothes and tools are sanitized so you don't move the problem around.
If you have a moderate to severe pest or disease problem, rotate your crops and do not plant members of the same family in that area for 3 years.
You can try solarizing in summer to try to kill soil pathogens in beds you have had problems with. Follow up with a crop that is not susceptible.
Happy gardening in Hawaii. Gardens are where people grow.