Father, this recently happened to my 10 yr old plumeria I have in my greenhouse. We went away for 2 weeks and spider mites moved in. They sucked the sap from most of the leaves and they all turned ugly and were dropping. I removed the worst of the leaves, sprayed it well with water, and then sprayed with Safer Soap. I'm keeping an eye on it now, but it seems to be doing much better.
There is always some type of problem with us growing our plants! I hope you can get yours back to healthy again. The small fan in the area is a good idea. I'm going to put another one in my greenhouse. I already have 3 solar vents and a solar fan, but apparently more air movement is needed.
