Sounds like they might have blight or fusariaium wilt, or verticillium wilt; are they growing where other solanacious varieties have been raised ?
You need to be cognizant of what garden varieties, or families have been planted, and where; that's why a home garden crop rotation map is helpful.
For Example :
the 'Solanaceae Family' includes: tomoatos, potatoes, peppers, eggplant; tobacco; and tomatillo.
If plants from the same family are planted in the same area/soil, there is a likelihood of passing a family disease along to the new crop.
By crop rotation, you minimize the possibility of having soil borne disease re-infecting new plants of the same family.(called: cross contamination)
The best online example of crop families that I have found for demonstration is found at Penn State :
https://extension.psu.edu/plant-rotation-in-the-garden-based-on-plant-families
An online example of sequence of garden crop rotation recommendations for the home gardener can be found at :
.. https://www.todayshomeowner.com/vegetable-garden-crop-rotation-made-easy/
This sequence of garden crop rotation maximizes the effectiveness of fertilization, while minimizing the cost,
since different plant types/ families have different fertilization requirements.
Unfortunately, I cannot rotate my crops as much as I’d like.
These two are in a corner of the garden where they will get sun mid day but not all morning. Nothing was planted there before. There are 5 Tom plants there, and the others are not yellowed. There are 4 other toms in a sunnier spot. I actually was picking spots for them a bit protected from the sun because it will get over 100 here for a long time. I’d like to keep getting toms all summer.
Looking at them now I think they aren’t all yellow, just 50% of the leaves. It’s just so noticeable.