Lo siento. The soil surrounding indeterminate plants large enough to fruit should be given deep mulch, light but thick, such as pine straw or leaf litter (not chips), and extend beyond the perimeter of the leaf line. Are you hilling? Hilling is a must in hot climates, especially with sandy soil, so stems can put down extra roots.
I grew up gardening in the tropics and, like you, close to the ocean. The sandy soil dries out fast. You may want to experiment with smaller fruited varieties that have genetic roots closer to the real deal like black cherry, yellow pear, or one of the "sweets" like Sugar Sweetie or Sweet Million. Everglades comes closest to a native tropical and, as I recently mentioned on another post, grew that one from childhood.
Why are you more shaded now? Are you using shade cloth? Most tomato varieties will not pollinate in high temperatures so whatever you can do to lower the temp is good. You are probably at the end of your season.
My tropical gardening experience was limited to growing in containers under trees, growing under shade cloth or in slat houses. Fall works if there isn't a hurricane and winter is a challenge because there is little rain. Maybe the best place to grow tomatoes is somewhere between Mexico and Minnesota? That's where I went.
My best advice is as soon as you see any sign of BER grab a couple of limes, a (preferably) home pickled jalapeno, an avocado (or two), a white onion, cilantro, garlic and salt and make pico de gallo. If you catch BER early you can toss the rot and use both green and red parts. It (BER) effectively kills the ability for the fruit to ripen beyond what was initiated. Trust me here. Make some tortillas, fillings and enjoy your space. Move on to chilies.
