The best fertilizer for Plumeria's is 10-50-10. We buy ours from Kelp4less.com. We use this fertilizer because not only is it rich in Phosphorus which promotes blooming, it also contains micro nutrients, something else highly beneficial for plants. Its so easy to use too! Simply mix the powder with the appropriate amount of water, drench your Plumeria's growing containers with it and you're done. We have great success using this fertilizer. Our Plumeria's bloom and grow much faster. We normally fertilize our plants once every two weeks, however, there is such a thing as too much fertilizer. If you notice your Plumeria's developing yellow spots on their leafs or slow growth. You may want to extend your fertilizing schedule to once every month or longer. 

Although the methods discussed on this page have worked for me, they may not work for you. Growing Plumerias successfully is all up to you, the grower. I'm not responsible for any damages that may occur as a result of following my methods.