Leaves yellowing from stem end
My tomatoes have been planted out since May 27th. All has been looking great till today. I have leaves on several plants turning yellow from the stem end mostly at the top of the plants. They weren't like his yesterday. I've looked through the problem solver and also searched GW but can't find a likeness to my problem. Actually the closest to me looks like salt damage but I don't see how that can be. The only other thing I can imagine is the farm field next to me was sprayed with a herbicide maybe 2 or 3 days ago. Gosh darn ... is there ever any relaxing growing tomatoes- oh yeah I know there is. Help very much appreciated - TIA
Here are a couple pictures.