The desert rose can be a fussy plant
Does not like too much water, especially after its' belly swells
Did the lighting change?
When it rains a lot, I have to bring the larger desert roses in under cover or the rain may kill it. When I bring it under the roof, the leaves fall off and go dormant until the season is over and I bring it back out to light again. It really doesn't have much to do with temperature as my winter temperature rarely goes lower than the low 50's. If I have a relatively dry winter as we have been having for the last three or four years and I keep the desert roses on their bench, the leaves will stay on through the cooler months.
I pot my desert rose in concrete and clay pots and I have a media that has cinder in it. Cinder is relatively easy to find here and it drains well. I also select a pot that just barely fits the roots. If my pot is too big, I have a greater chance of over watering it.
Are the leaves staying wet overnight?
Adeniums can get stem rot which is caused by a fungus and the rot starts at the leaf tips. The leaves will turn yellow, then brown and finally fall off. The tip of the stem will be brown and if left unchecked it will travel down the stem to the mainstem. It is one of the more common problems with adenium. If the tips are rotting, you can use a sterile pruner and cut back the tips until you get to healthy tissue. The ends need to callus off, so try to keep it from getting wet until then. The tip won't grow, but side branches will come out. I sometimes put wettable sulfur on the tips when I cut them. It is getting harder to find wettable sulfur now, but dithane is still available although mostly from agricultural suppliers.
Happy gardening in Hawaii. Gardens are where people grow.