Hi. So I'm pretty new with plants, and my other cacti seem to be doing okay but this one developed a large, really watery, mushy, yellow-brown spot that looked really unhealthy so i cut it off and so now there's a huge chunk missing of my cacti, and the bottom part looks like it is rotting? But the bottom part has been like that for a while now (I have had the cacti since the beginning of September) The top part used to be dark purple and had much of the pink flowering, but it looks all dried up now (lighter colour, even green instead of purple? or is the green a sign that it is reviving? haha I really don't know) and a lot of the pricks havee either fallen off or not very strong. But, there does seem to be growth coming from underneath. Oh, and I also found a bug on it today, but I looked around and in the soil and could only find the one. So I guess I'm just wondering if it can be saved? And what steps should I take? Also, should I place it far away from my other cacti? Thanks, Attached is the sad picture of what it has turned into and also what I think might be new growth.
i also think the draft from my window has affected my plants because all of them have some browning but I don't know where else to put them (I'm living in residence at university and have no other natural light source than my window and I want to make sure they get enough light every day) How much light do they really need? Hopefully someone can answer all of my questions. Sorry but I am new at this and figured this would be a good way to learn! :)