Please post an image or two.

In addition to that, please give us some history: Potting mix? or in the ground? Prevailing temps, night and day? And anything else you think might help us help you.

These tomatoes in containers are using soil made with approximately 1 part peat moss, 1 part mushroom compost, 1 part vermiculite, and ~1/4 cup garden lime to four gallons of soil mix. I water them daily, and they are grown in an SWC that I am experimenting with; plastic buckets, with an inverted colander at the bottom, and the soil mixture is held in burlap coffee bags. The discoloration only appears in the lower leaves, and these plants have been in the five gallon buckets for only ~one month.The temps have been in the 60s and 70s at night, with highs in the mid 80s during the day. I water them daily, and just fed them with tomato tone two weeks ago. They also get ~ 20 oz. of diluted Texas Tomato food every ten days or so.Any help is greatly appreciated, thanks!