I keep this in a sunny window, lately I’ve been seeing this brown shriveling in some sections of the plant. I water weekly with Schultz cactus food in the water. Any suggestions on how to bring back to health? Possibly I’m watering too often? Thanks very much.
You’ve got a couple different problems. One is that you are watering and fertilizing too much, causing the plant to grow too fast, rather than slow and healthy growth. Less water and a lot less fertilizer. Second, you appear to have mealie bugs on the plant. You’ll need to spray with an organic pesticide, like a Neem Oil.
You can prune off the dead branches and leaves and the rest of it should survive fine.