I saw some at HD year before last, and bought the lavender one. When I brought it home, it went downhill fast. The leaves started getting warty looking and falling off left and right.
I took it to my local extension office and the agent there couldn't figure out what was wrong with it either. The roots looked healthy.
She recommended using a fungicide, which I'd already tried. I had kept my receipt and ended up taking that plant right back and getting a refund, as it was 1/3 the original size by then and looked awful. Later research revealed that I should have taken it out of the peaty soil it was in, let it dry out thoroughly, and replanted in a gritty mix. It totally hates wet feet and needs to be kept on the dry side. Maybe I'll try growing it again someday.
At least, I've finally got the hang of the holiday cacti.