I'm still new to tomatoes, so perhaps Silvia or someone can give you a more extensive answer... but tomatoes need more than just generic fertilization. They require various micro-nutrients in order to produce good fruit. For example, a lack of calcium will result in bud end rot (nasty black spots on the bottom) and lack of magnesium can lead to smaller fruit. While my mother and I have the same kinds of tomatoes growing, mine are about double in size and the only real difference we could discern is that I augment my water with magnesium sulfate every other week. But along with the micros, the plants need to be able to them up. This means they need fairly regular watering and, if they are planted in the ground, nematodes can attack the roots making it harder for the plant to get the nutrients it needs.

I hope this helps with trying to figure out the problem.

I'm not a tomato expert either...But isn't it too hot right now for Tomatoes to fruit? I think they need temps below 72 degrees for blooms to set fruit...not positive on the exact temps but I do know that at least for me in zone 9a/b my tomatoes blooms/flowers stop setting around the end of May...maybe someone out there can tell us if this is true or not?

Beachlovinvol, in our Florida climate tomatoes have a life span, they produce when the conditions are right. My season in 9b has ended by me, the tomatoes plants that already had fruit on it were producing and the plants still look healthy but after the summer rains, the heat and the bugs, it is time for me to clean up because soon I will be starting another crop of tomatoes for the fall. The only thing that do well now are summer crops, tomatoes are spring and fall for me.
Some people choose to keep the tomatoes alive in the summer so hopefully they will produce when it gets cool down, but I rather start with fresh plants less bugs and disease this way.
It is easy sometimes to identify the problem when we can see a picture, otherwise is a difficult guess.
Don't be discouraged, there is always a new season to do better, experience is your friend.:)

Silvia

beachlovinvol - Since you are a beginner, I suggest that you start with the small varieties of tomatoes. A good one is a grape tomato called 'Julliet'. It is a great producer and is very disease resistant. It is one of my best performers. We are at the end of the spring tomato season. All I have left are the cherry and grape tomatoes and they are struggling now too.

Like Silvia mentioned, the fall tomato planting season is coming soon so you can start over. Gardening in the fall is more difficult so be sure to grow disease resistant varieties.

With some practice, you will be a good tomato grower. Just keep trying.

Christine

Here's an FAQ link from the Growing Tomatoes forum, note the temperature rangecolor> under which blossoms are viable, that should explain why we can't grow tomatoes in central or south Florida during the summer :-(

Tom