Hello Kris:
Tomatoes are heavy feeders, untilizing the nutrients in the container. I would suggest some additional fertilizer, either diluted in water and applied with your frequent watering or a granular material that will be dissolved when you do water. You can harvest frequently, allowing the plant to put the food and water into newly formed flowers and developing fruit too. You could also actually limit the number of flower clusters, again allowing more food and water into those clusters you do leave.
I hope this information is helpful.
Sincerely, Richard Hentschel