If it is anything like tipburn on lettuce which is a problem also with calcium, it may be that the longer days of summer cause the plants to grow faster than they can take up water and nutrients.
Variety will probably matter, I think a few people always get BER and I hardly have any on my heat resistant tomatoes which is mostly what I do grow.
Planting in self watering containers though, can really cut down on uneven watering issues. A five gallon reservoir is good. A tomato in full production on a hot day can drink up to 4 gallon of water a day.
Re: Vegetable disease/ soil sterilization help
Happy gardening in Hawaii. Gardens are where people grow.