Plumeria Branches Wrinkled. Freeze damage looks almost the same as stem rot. Water them thoroughly to help reduce stress on the plumeria which can also lead to a weakened resistance to pests.
The three largest the branches are getting soft and wrinkly the leaves are dark green and they have a few flowers. Early to mid summer is also good time. I have other problems also but need to address this one first.
In either case with mature plumeria just cut off the affected areas and a mature plumeria will bounce right back with new branches and leaves.
While some plumeria lose their leaves when the weather turns cool distorted growth leaf curl and yellowing are signs of an infestation of sap sucking insects like mealybugs spider mites or thrips. I have other problems also but need to address this one first. Again my plumeria is shaped like a y with one stem and two branches. Spring is the best time to start plumeria cuttings when the are waking up from dormancy.