I'm sorry. I've stated before that not once ever have I checked the Ph of any soil any plant and I do just fine. Being in Hawaii, you shouldn't have very many issues growing plumeria. Do you even NEED to water your plants there? I wouldn't try putting too much science into it unless you're trying control groups and such. If they are growing and healthy, that's all that matters. Give them sun and feed them. They will bloom.
