Have you had your soil tested or the manure? Or do you know for a fact that where you get your fresh cow manure from they use it on their pastures?
I ask all these questions because if you are simply going by plant signs and symptoms, it could be other things causing issues as well.
I'm not backing Grazon but it is part of our food stream now because almost every grazer uses it somewhere on their property.
Also, it is heavily used when crops are also grazed, which is becoming more common.
So it has been in our food for many years much like Roundup. I doubt we can point a finger at either as the absolute cause of contamination or lack of production or health in a given crop.
I worked for a spraying contractor when I was 16yo in north Qld spraying chiney apple and rubber vine among other things and got saturated in various chemicals every day. I'm still here, no cancer, just osteo from lack of estrogen unrelated to any chemical I was exposed to back then or since. I've never worn protective gear when working with chemicals.
I might prefer to have an organic garden but that doesn't mean I haven't worked with chemicals regularly throughout my working life.
When I was trying to work out what the problem was with my soil, I went through many iterations of possibilities until a local fellow who had been to uni to study mineral contamination in soils (mine is old gold bearing and very poor soil) was able to set me straight. Now I know, it's not such a scary thing, just inconvenient that I can't have the huge garden I'd like to have and sell organic produce on a much larger scale.
Pretty much every bag of manure or compost or garden soil etc purchased from a big box store or any nursery and made by any process that uses bulk ingredients such as fresh manures from sale yards, dairies, chicken farm, piggery or abattoir waste and similar will be polluted with various chemicals including grazon and roundup. Those two, as well as 24D, are endemic in our farmlands now. I have my own little personal store of them in my liver! Most likely from exposure as a young person. So I really don't think they are so terrible that they will prevent fruiting unless sprayed directly onto the plant by the person doing the gardening and I'm sure you aren't doing that.
If on the other hand, you watered your garden with the water from my dam, you would certainly affect your plants, they would cease to fruit and the leaves would certainly turn yellow. But it's iron that's the culprit.
