« Back to Organic gardening @ 3618
Tomato magnesium deficiency
Yellowing (or oranging, etc) older leaves, especially between veins, is a sign of magnesium deficiency. Plants need magnesium to make chlorophyll just like humans need iron to make hemoglobin -- and both molecules are required for all energy use and all metabolic function for their respective creatures.
The cure: Epsom salt (which is edible, soakable, and otherwise nontoxic to people) solution, sprayed on leaves every couple days. Makes them better in a week or so. The old leaves don't get repaired, but the new ones are nice and green.
Also: Planting them out in the garden, of course, where there's more room and nutrients.