Illness taking over my plants, please help!

[lakelady]

I am completely stumped as to what happened to my plants in one of my beds of tomatoes. Seemingly overnight, they went to healthy and green and lush, to browning leaves and I can't figure it out. I've been searching all day for online photos and getting bug eyed.

It started this morning when I noticed several plants not looking so healthy, a little wilted. This afternoon after work, holy cow, many more of them look bad and lots of leaves are turning brown. Not just the bottom, not just the top, sort of in the middle if you will. I have not sprayed any insecticides, my neighbors have not either (man across the street on the mountain doesn't even do any yardwork . This bed is directly along the side of the house below the road. One potted plant almost looks like early blight, but none of the others. The ONLY thing I have done, is yesterday I sprayed with Excel LG. Nothing more. Over a week ago, I sprayed with soapy solution and some neem oil, but it did not affect plants at all.

I'm really worried I could lose all these plants in a few days and also concerned that the other garden beds are next. I didn't have time to check them out before dark.

Any ideas at all???