While fertilizing plants is not a cure-all for disease or other plant problems it is a good idea for vegetable transplants.
For transplanted vegetables such as tomatoes, peppers, eggplant or cabbage, add a starter fertilizer to the water used in setting the plants to get them off to a faster start. Commercial starter fertilizers mix with water or are water soluble. Follow label directions, because mixing too much starter fertilizer can burn the plant roots.
You can make your own starter fertilizer solution by adding 2 tablespoons of ordinary fertilizer, such as 5-10-10, 3-12-12, 10-10-10, or similar material, to a gallon of water. Mix well with a stick or shake. While some of the larger fertilizer particles will settle out, enough soluble material will remain in the water. Use about 1 cup of this starter solution for each plant. Commercial soluble fertilizers also can be used as a plant starter. Follow label directions.