A couple of days ago, my tomato plants starting wilting from the top.  They are seemingly healthy one day, then severely wilted the next -- with the top being impacted first.  There is no indication that the plants are sick before they wilt -- no spotting or color change.  They are nice and dark and green, and drooping.  (Photos attached)

I removed the first two affected plants, hoping that whatever blight or bug was causing the problem would be removed as well.  No luck, through.  Two more plants started wilting today -- since morning watering.

When I removed the dying plants, their roots still seemed firmly in the ground.  The garden is surrounded by lawn - not high weeds.  There is a walnut tree in the area, but the garden is well beyond the drip line.  A few leaves might have gotten tilled in last fall, but very few.  I've been watering them every day -- it's been fairly warm and dry.  The soil had pretty good drainage.

Any suggestions would be very much appreciated.  I've lost four plants in two days and at this rate, I'll lose them all.

Dean

The attached photos show 1) one entire plant, showing that the top is wilted and the bottom leaves look much better.  Also, there is no discoloration or spotting, and 2) a close up of lower leaves shows that some leaves look OK, while leaves from the branch above are severely wilted.