My tomatoes get some sort of fungus every year. I think it's either fusarium or verticullum. I even bought Rutgers VFA seeds this year, which are supposed to be resistant. There is no good way to get rid of this fungus. It will slowly destroy the plant. You can slow its progress by pinching off and discarding infected branches.
Apparently, the best ways to prevent it are rotating crops, sunning/tilling soil during winter, and possibly bleaching the soil. I don't think I'm ready to get that serious about it, especially since we have to travel to get to our garden plot. Perhaps I'd be more aggressive if it were in my own backyard. I'll still get plenty of tomatoes out of these plants before they finally die.
We've gotten four large cucumbers off this one plant. I'm happy that it hasn't yet fallen prey to the verticullum wilt it usually gets from cucumber beetles. It's just starting to show signs of wilting.
This has been one of the hottest summers on record in DC, so we haven't spent as much time on the garden as we should. All of the plants have suffered, but I have been very inattentive to the basil. Typically, when annual herbs start to flower, it signals the end of their life. This is true for basil, cilantro, dill and others. (Perennial herbs like sage, oregano and thyme will flower and grow bushy, but they'll repeat the process year after year. You should cut these back after the growing season.)
Anyway, the annual herbs perform better and longer when you pinch off the flower buds as they appear. In the case of basil, once the plants start to produce flowers, the leaves will get really small. They'll still be usable, but they're more annoying to pinch off to make your pesto. In order to get the nice, big leaves like you can buy at the supermarket, you need to keep your basil flower-free.