I have a fish hook cactus...he stays indoors mainly except for some warm days in the summer. Last year my cactus developed a few bronze colored patches on some of the ridges. I thought that they were sunburn spots. Over the winter the spots have grown and are now a lot larger. I've consulted several books, but have not been able to figure out what they are or how to cure this problem. If anyone has any suggestions it would be much appreciated. Thx.