When you say black spots, do you mean small black spots or big black spots? Were these plants indoors and you moved them to outdoors? Sometimes when you move an indoor plant outside into direct sun, it will become sunburned and that scorch will turn black.

The awful humidity and heat from last weekend and the early part of this week really did a number on a lot of plants but with the current weather you should see some improvement. To avoid fungus, make sure the plants have good air circulation and water when the soil seems dry to the touch.

As to the watering, if the soil is dry and the plants are wilty-looking, water them. If the soil is wet and the plants are wilty-looking, don't water them. My rule of thumb...generally, if you're happy with the way they look like in the morning, you're doing something right. If they look droopy in the morning, something's wrong.

If the soil is VERY sandy, consider adding organic matter (i.e. compost). I gardened at the shore (Asbury Park) over a decade ago and found the soil to be on the sandy side but quite lovely to work with and my plants thrived. Much like the soil where I grew up on Long Island. I am now in Essex County and the soil has much more clay. Needs much more compost than my beachy gardening days.