If you’re purchasing your compost or manures (or even topsoil) be aware that herbicide residues do exist and can create conditions that restrict the growth of plants.
For example, aminopyralid is registered for a wide variety of crops and has created enough problems in the UK to have its registration pulled (technically Dow asked to have it pulled)
Having said that, the residue does persist in manure and composts so if you purchase products with residues, you might see stunting and leaf curl on susceptible plants such as tomatoes.
This would be early in the season and not later. So as soon as the plant roots start to grow out of the starter media and expand into the soil, they’re going to do poorly. If you’re seeing later problems, it is something else.
As a note, tomato seedlings are great starter plants for testing of almost any kind of herbicide residue – darn near anything will kill them and they’re a marker plant for that kind of testing.
So if you’re not sure – try some tomato seedlings in new soils.
This is one more reason to produce your own compost to encourage micro-organism spread. Organic matter can be obtained from other things – from peat to leaves (it’s about time to go hunting for all the leaves nobody else wants) to purchasing straw.
In any case, it was a lesson remembered for me and I thought I’d pass it along.