Christmas cactus has brown spots and some leaves are limp. It is not growing as fast or well as I would like. (Looked much worse this summer.) Thought I had lost it. Then it started growing some new leaves and bloomed rather nicely just before Christmas.
Christmas Cactus Brown and Limp
Certified GKH Gardening Expert
This is a sign that the plant is overwatered. Christmas cactus should only be watered when the soil is dry at least one inch down into the soil. Your soil may be holding onto too much water as well. Repotting the cactus in a cactus soil or a potting soil with additional sand or perlite added will help. Here is more information: https://www.gardeningknowhow.com/ornamental/cacti-succulents/christmas-cactus/limp-christmas-cactus.htm