I live in central Florida and have had this potted plumeria on my covered balcony for just over one year. It is potted in a well draining soil mixture, watered 1x/week with liquid soluble Hawaiian Bud n Bloom 5-50-17 fertilizer, and receives partial sun. The plant was growing really well until about 6 weeks ago when some leaves began turning yellow, acquiring brown spots, then dropping. Any help here would be appreciated! Thanks!
The majority of Plumeria are deciduous so it's not surprising that the leaves are falling off. It's how they do. There are a few (at least one) species that keeps it's leaves year-round.
There is a lot of good information on Plumeria culture like this:
I've never had luck with Plumeria, I live in the wrong climate. When I was a kid we had a large Plumeria tree in the front yard. It was awesome.