Gvelazco: Welcome to the forum. While I certainly am not an expert on Plumerias, I have been keeping more than a dozen alive for over six years now, inside under lights in the winter and outside in the summer, all from Thai seed. One of these years, one will bloom, and I am certain I will have a major cardiac incident if and when it does! Having said that, I carefuly looked at your photos, way different from any other photos submitted, and indeed, in my humble opinion, your Plumerais are indeed sick- BUT, not from insects, but from over watering??? OR over something, perhaps fertilization. Immediately, when I see a number of yellow leaves on any of my plumerias, I know I have been overwatering!! One can easily rule out spider mites or any other infestation by just holding the plant up in front of a strong light. Very simple solution: Pull one out gently -they have a very small root system, and check the soil mixture. Is it overly wet? If so, repot it in new soil, and regulate the amount of moisture it gets- via rain, personal watering, etc. I just repotted my dozen or so Plumerias, and all my Adeniums (24 or more), my one Persian lime, and four Bouganvillias, and in almost all cases, the plants were all on the dry side, (we had no rain this Summer), and not a yellow leave to be seen anywhere. If you and nature combined, have been guilty of overwatering, you will note that at the soil level, the plant is getting "soft" and if so, that undoubtedly is from too much water, regardless of the source. I only ever saw a live Plumeria in bloom in Cuba (you guys aren't allowed to go there") LOL. and it was absolutely beautiful. Certainly worth the effort, in any zone or country!! Cheers!
