I never recorded when I start fertilizing so  not sure if I'm early or late this year.  I use that Miracle Grow 3-1-2 blue water soluble fertilizer that comes in packets.  One scoopful into a two gallon bucket is good for 2 1/2 tomato sized containers.  My main concern are the tomatoes -- the only plant that has been a perpetual failure for me year after year.  Everything on the main roof was fertilized and all house plants on the veranda.  I'm debating whether or not to expand the fertilizer regime to other plants.

I normally try and fertilize once a week.