Here the 1874 RLDS edition accidentally omitted the word all; the 1908 RLDS edition restored it to the RLDS text. Another example of this same loss of all in the 1874 edition can be found in 2 Nephi 9:14 (see the discussion there for the loss of the all in the phrase “all our guilt”). Clearly, “all their sufferings” is perfectly fine here in Alma 20:29; in fact, there are two other instances of that phrase in the text (including one in this same section of the text):
Summary: Maintain in Alma 20:29 the occurrence of all in the phrase “all their sufferings”.