Fertilizing is a very "users own experience" type of thing, as Hetty has shown. Most people are very particular about what they are using. It also matters if you have potted/in-ground plants. Hetty and I both live in an area that is very suited for plumeria growth, and that definitely plays a factor. By saying that I use a high middle number fertilizer, I do not mean 50+, but I do use a good 25 - 30 Phosphorous mix for my plumies.
Like stated in my original post, it would be helpful to know what kind of soil you are using, and what kind of sun exposure they are getting. Also, how old are your plumeria? When were they started as cuttings? Some plumeria do not bloom too frequently until a certain age.
p.s. That is a very beautiful tree, Hetty.
