Am growing 3 tomatoes in a plastic gallon too, and it grows to almost 2 feet now, i am wondering if I can see fruit of it soon, hopefully. The challenge here in the city is almost the lack of compost or source of organic materials. Cemented everywhere here, but still not stopping me to plant. Good luck to my herbs and yours too.
I made a compost pit in a pail a couple of months ago. It reduced the waste in our household to 1 bag per week, and my plants are using the soil now. You might want to give it a try. :-)
Yes, I do saved my kitchen scraps , but it takes longer to rot without soil in it. So I made it like a compost tea and use it to water the pots.