Hello everyone Its my first post on this site so im just hoping my picture link works...its a browning on my cactus? . I don't over water or over feed and iv just added some good bacteria to the medium...its been like this for a few month but is slow and starts where the spikes are? I know about nutrient defects/ toxicity about other plants but not about cactus......
The only cactus I see in the pictures is the one with the yellow spines, but I assume you mean the tall, thin plant, which is an Euphorbia. Most of it the browning look like normal corking, but the bigger area with the grey patches looks more worrying. It is not easy to say what is going on there or how dangerous it actually is, as the picture is a bit fuzzy (the camera has focused on the background instead of the plant). If it continues to spread you may want to consider cutting off that stem.
hope this picture is better. The grey bits you mentioned....there just abit of dust lol. https://onedrive.live.com/redir?res...authkey=!AN1xYlrdQ6AN1-Y&v=3&ithint=photo,jpg
Corking is a lignification process when parts of the stem turns to wood, which is necessary to support the increasing weight as the plant grows. This usually happens at the base of the plant, but sometimes higher up as well. On second thought, the brown spots could be scar tissue after damage caused by disease or some pest. Corking usually does not occur around the spines like on your plant, but I have not grown Euphorbia in a long time. Not much to do about that unless you can a) see insects or mites close to the damaged zones (some of these are tiny, a magnification glass is useful) or b) it spreads.
