Here in the original manuscript, Oliver Cowdery initially omitted the repeated their; virtually immediately he supplied it, inserting it supralinearly (there is no change in the level of ink flow). Either reading is theoretically possible, so the critical text will follow the corrected reading in 𝓞. There are three other examples of the repeated determiner for conjuncts of sign(s) and wonder(s):
The natural tendency in English is not to repeat the determiner for such conjuncts. For further discussion, see under conjunctive repetition in volume 3.
Summary: Follow the corrected reading in 𝓞 for Alma 37:27: “yea and all their signs and their wonders ye shall retain from this people”.