Actually, South Florida soils vary a lot--- one should not generalize muck, sand, shell rock, and limestone soils.
The sandy soils in eastern Palm Beach county, ancient sand dunes, are mildy acidic--- when they are not mixed with construction rubble, shell rock, or other bad fill, and are not watered with high pH water. Correcting iron deficiency here, and also in many nursery potting soils, is most effectively and economically done with Sequestrene 330 or equivalent products.