Answer: Generally speaking it is not a good idea to allow cat waste to accumulate in vegetable garden soil due to the risk of introducing pathogens carried in the waste of meat-eating animals.
But I can't think of a reason why it would have affected only certain plants, unless the there was fresh waste in contact with the plant's roots.
I would recommend running some soil tests to check the overall fertility and pH of the soil to see if something is out of balance there.
Also, without knowing your general location, it is difficult to tell if the spring/summer weather may have affected your plants. The early season/cool season growers -- lettuce and peas -- did fine while your main summer crop is doing poorly. Stunting can happen due to excess heat or drought, to overwatering or excessive rain, or to planting too early or too late, or to nutrient problems or to a variety of other factors.
You might want to consult with your local county extension and see if they can help you trouble shoot. They should be able to help you with the soil testing and interpreting the results as well.
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