Why are my tomato leaves turning yellow?

Gardeners, many of you have grown tomatoes at home and will understand my description of how homegrown tomato tastes. Homegrown tomato flavor is intensely rich and tangy, having a pleasant balance of sweetness to acidity, and where the fruit is juicy. It is my opinion the homegrown tomato flavor exceeds the ‘ho-hum’, bland tasting supermarket tomato which has a mealy (grainy) texture. Of course, t…