The 1892 RLDS edition unintentionally replaced the plural labors with the singular labor. The RLDS text has continued with the secondary labor, even though 𝓟 reads in the plural; the word is extant in 𝓞 and reads in the plural.
Elsewhere the text has six other examples that refer to performing labor, of which one (marked below with an asterisk) parallels the language here in Alma 53:1 (both read “perform their labors”):
For each case of “perform labor(s)”, the critical text will follow the earliest textual sources, thus labors here in Alma 53:1 (the reading in 𝓞, spelled there as labours).
Summary: Maintain the plural labors in Alma 53:1, the reading of the earliest textual sources (including both manuscripts).