I live in Seattle, less than 1 Km from Puget Sound, so temps a little cooler than average for the city. I have three tomatoes growing in containers on my deck. One is suddenly developing some yellow leaves in the last couple of days, mostly leaves just below half the height of the plant. Green color is fading uniformly from leaves, no spots or curling. It is cultivar Sungold. Watering once a day, not so heavily that water comes out the bottom of the pot. Sprinkled foliage with compost tea twice, a week ago and two weeks ago. Otherwise not fertilized yet. The plant is still growing vigorously from upper shoots and setting fruit. The lowest brace of fruits is ripening now. Two others, cultivars Bloody Butcher and Black Prince, treated similarly show no signs of this yellowing. Any hints?
Tomatoes don't like too much water. I let the soil surface almost dry between waterings. But I haven't grown tomatoes in containers, so my suggestion might not be good for your case. Plants in containers certainly need more frequent watering.
