Technically speaking, you should not eat the tomatoes or other vegetables that might have been contaminated. Testing has not been done to determine how much of an herbicide like 2,4-D is safe to consume. We have had a lot of disease problems with tomatoes this year so the vines might have been killed by a disease rather than the spray. But, if this were the case, it is likely that some plants would still look better than others. Also, if it were an herbicide, I would expect to see damage on other plants besides the tomatoes, so it is possible that the herbicide was not the cause.  But, without chemical testing you cannot be sure.