Certified GKH Gardening Expert
The environmental requirements for these epiphytic shrubs is like that of an orchid. They are quite strict.
There are a number of things that can be causing this, so knowing their care requirements will help you to start sorting out the issues at hand.
This article will help you with their care:
https://www.gardeningknowhow.com/houseplants/medinilla/caring-for-medinilla-plants.htm
I have been growing successfully orchid plants and medinillas of all varieties for over 20 years and indeed know their cultural needs. Accept and express my gratitude for Bushdoctor’s referral to an interesting article; but I still need a more specific reply or comment to my question.