Here the 1841 British edition accidentally omitted the definite article the from before Lamanites, thus creating an indefinite reading that is highly unexpected in this context. The subsequent LDS edition (1849) restored the correct reading, “and thus were the Lamanites afflicted also”.
Summary: Maintain in 3 Nephi 1:30 the definite article the before Lamanites, the reading of the earliest textual sources (𝓟 and the 1830 edition).