I have seen over-watering and underwatering that can cause those symptoms as well. Tough to diagnose with all of your others doing well in the same conditions. Definitely doesn't look like an infection though. I used to grow tomatoes, and had a similar issue, turned out to be a deficiency. "Fruiting" or "flowering" plants are usually similar. I wish I cold be more help.
Take a good look at them when you harvest and note how the glands look (size and amount) compared to the others. They may turn out to be fine.