Before you fertilize I'd recommend a soil test, especially for vegetable gardens so you will know exactly which nutrients your soil is lacking. This way you can add the appropriate organic fertilizer necessary. I like to say you get out of your garden what you put into it...in other words if you want organically grown vegetables use organic fertizers and if you want chemically grown vegetables use chemical fertizers. Plants really don't know the difference and they will take up what nutrients they need. But if a certain nutrient is missing that is needed for the plant to take up another that could be a problem, that is why soil tests are so important.

Also, the soil test will tell you ph. I believe the ph is important because it can inhibit the uptake of certain nutrients. Meaning that even if the nutrient is in the soil, the plant is unable to use it.

Penn State Extension does soil tests for about $9 (I think) I will put the link below.

Here is a link that might be useful: Penn State Extension Soil Lab

Thank you both! Will somebody come to my house to perform the soil test or will I receive a testing kit to take care of myself?

You can have more information about chemical fertilize for tomatoes on Haifa'site:

Here is a link that might be useful: tomato plant fertilizer

Some chemical ferts have salts in them that organic ones don't.