I've been growing cherry and grape tomatoes in 5 gallon containers for years, and always have the same problem. They start off great, but about 1 and a half to 2 months into the season (July) the leaves start to brown up and die off. I still get tomatoes, but there must be something about the containers or watering that causes this browning. I live in NJ. I water every day. The containers all use potting soil that specfically mentions suitability for vegetables. I drilled drainage holes in the bottom of the containers and put stones at the bottom.
I grew one plant this year in the ground and that one has not browned up.
I fertilize with tomato food every 10 days or so per label directions.
Any clues as to why the container plants have this problem every year? I'm sure I'm losing a lot of yield because the foliage does off so quickly in mid-late season.