Hi Glen and welcome. I think almost everyone who grows orchids will have a different answer for you as far as fertilizers go. But I have also read that the urea issue has been disproven.
I have a couple of orchid books written by very knowledgeable people here in Florida. One is a professor emeritus in Env. Hort. at UF, Thomas Sheehan, who has been growing orchids in a greenhouse for 50 years, and he uses regular old Miracle Gro in a hose-end sprayer every two weeks. He says he has great results doing this. He varies the strength of the fert according to the seasons, because of course we get more temperature variations here than you do in Hawaii. Very dilute fert in winter when we get nights down into the 40's, and much more in summer when the nights never get below 80.
The second "authority" is Dr. Martin Motes who grows orchids commercially in South Florida. (his doctorate is in literature, not anything plant related, but he still has been growing orchids for many years). He got into much more in-depth analysis of fertilizing than Tom Sheehan. Our first issue here (and you might have it there, too) is phosphorus in the water. Our water, both tap and well water, has high levels of naturally occurring phosphorus, and it reacts with metallic elements in fertilizer like magnesium, potassium, and other trace metals making them unavailable to the plants. This is especially critical to foliar feeders like orchids. So he recommends using formulations with a very low phosphorus component (the middle number of the big 3) for regular feeding of orchids, and only in springtime to use a high phosphorus formula to stimulate root growth and flower formation. He also advises to correct the pH of any water you use on orchids to a neutral 7.0 or even a bit lower, to again make all the nutrients readily available to the plants. Or, use nothing but rain water. His other important advice is to boost the magnesium in your fertilizer by adding Epsom Salts to the sprayers regularly.
Even though you aren't in Florida, I'd recommend you get a copy of his book "Florida Orchid Growing, Month by Month" for his detailed recommendations. I've adopted a much better regimen for my orchids since reading it, (both fert, and pest and disease issues) and everybody's growing SO much better now. The book's available from Amazon.
