Hi this is great lots of info coming through. I have moved house , well about a year ago, my hoya' s get buds, but they drop off. cant understand it , they use to do so well in my old house, and my varigated one has all ,but a few leafs, reverted to green. perhaps its not such a good year here in the uk.
Bud blast might be because the soil is too dry while the plant is in bud, also, the may not ne high enough. The light should be bright with some sun. If your variegated hoya is turning green, it's not getting enough light. Try giving it some direct sun for about 3 hrs, but you might want to move it to more and more light gradually.
I have a variegated few as well. I actually cut off the all green shoots because they take up most of the plants energy. If you dont cut them off it will eventually revert to all green.
Variegation is a form of mutation/virus and unstable which I always thought. The variegated leaves takes energy away from a plant making it grow at a much slower rate. I was told one time that I should really take off ALL the variegated leaves on a carnosa so it would grow better/faster. Well, I reluctantly went and cut them off, then regretted it! I bought it for it's variegation! It's now growing again and I have been leaving it alone to grow the way it wants. It's slow, but that's ok, I mind at all! Variegated plants will revert back to all green due to lack of light and sometimes for another or other reason, although I'm not sure what that is, bad breeding? Cloning? My variegated yellow and green Christmas cactus I used to have turned back to all green and that was getting very good light. The green and white variegated Christmas cactus does not revert. The all green sections of many variegated plants are more vigorous and will eventually take over the plant if it's in low light.