I have no experience gardening in humid climates like yours, but I would suspect that either your soil is too hot, meaning it's too fresh and can burn plants, you have some sort of fungus, or the grasshoppers are taking bites out of your tomatoes before you can. If it's a problem with the soil (compost or fungus) you'll see burn marks, strange spots on the leaves, or the plant will look wilted regardless of how well watered it is. As long as your soil doesn't have high clay content, it's unlikely that you'd over water a tomato plant.
Definitely post those pictures for us. Here's the URL for your county extension office:
http://hillsborough.ifas.ufl.edu/ I simply typed Tampa, FL agricultural extension office into my search engine. You can take courses from them, take them samples of your dying plants and have them identify the culprit, get on a mailing list to know what pests and pathogens are hitting your neighborhood, etc... In fact, one of the first things I saw on the website above is that they are offering a solar cooker class next week, get on it!
Another thing that works for me a lot of the time is plugging key descriptive words into your search engine. For example, if I notice my tomato plant has black around the edges of the leaves and black spots in the middle, I type "black spots black edges tomato leaves" and the first few hits tell me that my tomatoes probably have a type of blight.
