The owners of Songbird Organic Farm in Unity, known for its heritage Maine grains, have stopped sales and pulled their products from store shelves after learning that the farm’s well water, soil and produce have tested positive for toxic substances known as “forever chemicals.” The contamination likely occurred when the farm and primary lease field were licensed for the spreading of biosolids in the early 1990s, according to a letter owners Adam Nordell and Johanna Davis posted on the farm’s website.