For us here in places where winters get really, really cold (below freezing for months at a time), we bring them indoors. They go dormant and we return them outside when the weather warms.

Here in Pennsylvania (in the USA, as I get the feeling you're not), they're in storage from October through May, or about half the year. They do just fine, although some people keep smaller plumeria under lights in winter. I did that with mine when it was small.

A friend of mine kept hers in her cellar during that period; it was huge. Eventually, she donated it as it got too large for her to handle. I did the same with mine.

where are you.. big city name...

how about a pic or two .. of the good and the bad ones ...

try to also include some pertinent info about the plants.. other than they look bad ... e.g. potted..media.. how you water them.. fert ... outside for summer.. etc ...

if you want to know where you might have gone wrong.. we need to know what you did to suggest otherwise ...

ken

You stored them too wet? Or too cold?

Hello. Sorry for the lack of details. I’m in Ca. 9a/10a hardiness zone. I brought all my plumerias in first week of November. I didn’t water them 3 weeks prior to that. I make sure that the soils is dried. The rots happened in the middle of the stem and not at the root. Because that I couldn’t savage them as the stem is too short. I lost one cutting due to black tip rots. I also have two cuttings that is wrinkle and soft to touch. 😩 I’m slowly trying to bring them out of dormancy by slowing introduce them to the sun and then bringing them back in the garage as spring is only a month away.

That's odd, because you did exactly the right thing, I think. If you stored them indoors, with temperatures around seventy, that was absolutely perfect.

Yes. I was shocked.. especially the black tip rots… I could have saved that one had I caught it early. Wish I had check on it more often..😩 now I have to look for the rainbow colors plumeria.