This is my first time growing tomatoes and they were doing great. However, I noticed today that the leaves are darkening, almost black. We did have a lot of rain last week, is that it? I checked the plants for bugs and didnt see any. I'm growing 5 plants in containers and it only seems to be happening to 2 of them. They are in an organic soiless mix and I've fed them with fish/seaweed emulsion along with a little tomato tone. Can I fix them?!