Well I'm having a problem with my fairy castle cactus. The problem is some of the tips turned yellow then developed brown spots. It may be because I left it outside most of the first week in december. But I'm also worried it might be scale. It doesn't quite look like scale though,The brown spots aren't raised and there flat against the skin of the cactus. Here are some pics what do you think? Also I just found out something about the spots, The smaller spots are underneath the waxy skin I can't pick them off. But I can pick off the larger ones. I just looked at both sides of one with a magnifying glass and it's a solid brown on both sides. Doesn't look like a scale insect. But I don't know for sure.