The phrase "leached off" refers to the process of a substance being slowly removed or drained from a material. There are several synonyms for this term, such as extracted, drained, removed, sucked out, and siphoned off. Each of these words implies a gradual or sustained removal of a substance from a source. For example, one might say that the nutrients were extracted from the soil, or that the water was siphoned off from the swimming pool. Overall, these synonyms suggest a deliberate or natural process of removal that happens over time, rather than a sudden or forceful action.