O-Kay--- Now, for me, a yellow flag goes up every time someone says they water daily. I realize you're in FL and the watering requirements may be different, and other FL gardeners can straighten me out, but most of the time, a garden -- an in-the-ground garden (containers are different) -- shouldn't need to be watered every day.
It's a good practice to water DEEPLY. Stick your finger in the soil, dig with a trowel, put out containers everywhere if using sprinklers, but you need to get a good idea of how FAR DOWN the water seeps into the soil after watering, or how many inches of water you are giving.
If you only surface water, you train your plants to keep their roots near the surface, then they dry out faster along with the surface soil.
This might NOT be your situation, but I just wanted to point that out.
What variety sunflower are you growing? ...And maybe you could describe the kind of locations you've tried growing them in. Maybe this just happens because of your location (as in FL), too.