Sounds like you have what is called Blossom End Rot. I think it happens from a lack of calcium. I googled it for you. Check out the item that starts with blossom end rot and calcium by www. caes.uga.edu. This should help you out.

Thanks very much. Would that also cause them to be hard?

I don't really have anything to add to what Zackey said, except that I had trouble finding the article that Zackey was referring to, so I linked another one below. I hope that helps you out.

Mostly I wanted to say "hi" - I am also in Panama City!

Here is a link that might be useful: IFAS - Blossom End Rot

That was a good article! The writer was our county extension agent when we live in Vero Beach. He was great. Whenever I do research I keep finding articles he has written. I wish he was our county agent up here! I don't know what causes the fruit to be hard.

I am in Tampa, but for the 1st 2 years of gardening, the same thing would happen to my tomatoes. The newspaper had an article about blossom end rot- suggested adding calcium &epsom salt to the soil- a couple of Tablespoons every few weeks- that has solved my problem.

Thank you all for the feedback and the articles. I am thoroughly confused, however. I added about 1/2 cup of gypsum to my 5 gal. bucket before I planted. Was that not enough? Do I need to add a little every few weeks? What does the epsom salts do? I'm also still wondering what makes them so hard. Thanks again for everything.

Irregular watering can "lock up" the calcium in your soil making it unavailable to the plants.

ginia 2009,
Epsom Salts is magnesium sulfide. It contains magnesium (10 percent) and sulfur (13 percent), Epsom Salts is a fast-acting mineral fertilizer that you can apply on the soil in a granular form or dissolve it in water and spray on leaves as a foliar spray. Tomatoes, peppers, and roses love this stuff.

Another good source of magnesium is Dolomite Lime, which is high in calcium (46 percent) and magnesium (38 percent), This also will add magnesium to the soil as you are using the lime to adjust the PH of your soil. Use mixed into the soil usually prior to planting.

Your tomatoes are hard possibly due to the improper balance of the different minerals in your soil.

I'm going to try adding some of these things. I'm thinking my system of watering may also be wrong. I've been using the sprinkler & have read that this is a no-no.
Thanks again everybody.