This is more than likely sun-related. I often see the same thing when I bring my plumeria out of a shaded greenhouse into full sun. I try not to do this though. I typically will move them from the greenhouse to a part of the patio that is shaded by the porch after noon. Every few days I will gradually move the plumeria plants away from the porch and into more and more full sun. By day 7-14, those plumeria will be in full sun.
