What's wrong with these tomatoes?

[Jeff23703]

For the past month our tomatoes have been getting worse and worse, but didn't get very bad until a week ago. I thought it might be the heat and humidity so I left them alone. I've looked at all the problem solvers and nutrient deficiencies but can't seem to find a symptom that fits exactly. We have spider mites which lay siege to the gardens every year without fail. I've noticed recent flea beetle damage. Luckily, only a few worms have been found. Septoria and spider mites were a huge problem for the potted plants, which were yanked out and thrown away a month ago. Oddly enough, very similar symptoms can be found on plants almost 100ft away.

The symptoms include:
*Random leaved branches drying up seemingly over night, they're still green too (except for those that dried a week ago, which are brown now). No lesions to suggest fungal attack. The drying seems to start at the base of the branch (or even just one side) and works its way outward.
*The main stems are turning coppery and then brown. The plants are still producing suckers and new branches, but very very slowly.
*After slicing through a stem, it appears to be green and healthy, except for the very outer part directly under the "skin", which is either ever so slightly brown or discolored green like the "skin", but the vascular tissue seems healthy. There is absolutely no wilting.
*The drying of the branches is centered around the upper middle of the plants and spreads from there.

All of these symptoms seem eerily similar to what happened last year when the store bought plants keeled over in a couple of days.

Any ideas? My father's plants are just as green and healthy as can be. He has no spider mites or flea beetles, so I'm wondering if that's the problem. I'm tempted to cut the plants back to the tops of the cages, spray with fungicides and pesticides and hope that the suckers and little branches develop and fruit before frost.

Jeff