I have 18 different varieties of heirloom tomatoes in containers. The majority of the plants were started last August and made it through just fine. I've already harvested quite a bit of tomatoes. All the containers are at least 10 gallons or more. I don't use any pesticides and used a tomato fertilizer last summer and a couple of weeks ago. The problem occurred before the last fertilization.

The problem is the leaves are starting to shrivel and dry up. They appear a little "rusty" and almost look scorched. Our temps here with the exception of yesterday and today have been in the 70's & 80's. I have sections of the plant that has new beautiful growth and then sections that look like this:

The fruit that has already set doesn't seem affected, but the flowers that have set are dried and brittle. I have searched for insects and didn't find any. I don't know very much about gardening except what I've read on this forum!

Please help me.