50+ Cactus Brown Spots. Fortunately, this is not a death sentence for your plants. Cacti plants can turn brown, yellow, or even purple for different reasons.
Why Is My Cactus Turning Brown Quora from qph.fs.quoracdn.net
Few legal plants are as controversial in the world of gardening as the popular moon cactus. Fortunately, this is not a death sentence for your plants. Growing cacti is not really difficult and can be quite rewarding.
I thought the spots might be from root rot, but it was hard to tell.
With the sufficient lighting, the right soil mix, and proper watering, the cacti will do all the work. Browning is a relatively common problem that many cacti gardeners have to deal with. Then once you start removing the bad spots, you realize that it's much, much worse on the inside than it looked on the outside. If you're new to the wonderful world of cacti, it can be alarming when parts of your beloved plants begin to turn brown.