Each bow lost its spring; thus the use of the plural springs with bows will work, although in modern English we expect the singular when referring to an essential quality of a tool or weapon, even in the plural (as in “the strings lost their tension”, not “their tensions”). Here in 1 Nephi 16:21, the 1953 RLDS edition changed the plural to the singular spring, but apparently the plural reading of the original manuscript is the intended reading.
Summary: Maintain the unusual, but possible, plural springs in 1 Nephi 16:21.