The affected plants are not growing like the others. They have stayed the same size and haven't sent out any suckers. I uprooted one, and the roots look fine. I have grown tomatoes in this spot before and they grew wonderfully- 4 years ago. We put the kids playset on it for the last two years and I think it was Lima beans I planted there the year before that. My next step is to do the soil test, but I haven't been able to go get it yet. I have noticed that the affected plants are either turning the slightest bit yellow, or in other cases, the newer foliage is quite purple. I have noticed that the plants that are affected seem to have set the most fruit beforehand. I don't know if this was a survival mechanism or caused the stress. Between irrigation (unfortunately we have to use city water) and quite a bit of rain (for here) in the last two weeks, I know lack of water isn't the problem. Cool temps would be the only environmental stressor.