I mostly grow veggies in containers and was also told feeding them was very important. I use Gro Power Plus, as recommended by several folks at our local, family-owned nursery. It is not certified organic, but it is a technicality issue as far as I know. (I haven't investigated it myself, but have been told this by various people.) This particular fertilizer is meant for the initial growth when the plants are getting started. It has high nitrogen.
Once the plant is established, then I have been advised to switch to a fruit-enhancing fertilizer. I have Dr. Earth's azalea fertilizer for my blueberry bush, but haven't gotten to that point for the other produce...yet.