Here scribe 2 of 𝓟 wrote “changed of their carnal and fallen state to a state of righteousness”. The occurrence of the preposition of with the verb form changed seems to be an error, perhaps the result of the immediately preceding “born of God”. Oliver Cowdery, apparently when he proofed 𝓟 against 𝓞, replaced the preposition of with from, which agrees with usage elsewhere in the text:
It is true that originally in English the preposition of meant ‘from’, so one could theoretically argue that the of here in Mosiah 27:25 is correct. But since of never occurs with the verb form changed elsewhere in the Book of Mormon text, it seems more reasonable to assume that of here is a scribal error rather than having the archaic sense of ‘from’.
Summary: Accept in Mosiah 27:25 Oliver Cowdery’s replacement in 𝓟 of of with from in “changed from their carnal and fallen state”, which is probably the reading of the original manuscript (no longer extant here).