Thanks for the feed info, guys! I need to start dosing my blueberries a little heavier, I'm seeing nice top-growth from the little supplementation I've already done.
Have either of you seen any sensitivity of Vaccinieae to nitrates? Some online sources say blueberries are lacking in nitrate reductase enzyme and will suffer or die if fed high nitrates for a long time. Not sure what precisely constitutes 'high nitrates' nor how immediate or reversible possible effects would be, and of course the bulk of the research to date has been on temperate terrestrials and so may or may not pertain to the tropical epi/lithophytes, which seem likely to have somewhat different rhizosphere conditions and associated microbes.
Chris, the obvious success of your plants on the nitrate-containing Better-Gro fertilizer does suggest it's not necessarily an issue for (all) the epiphytes, or at least not an immediate and/or serious one. Relatively light applications may also prevent a buildup to potentially toxic levels, whatever those may be. I'll try to dig deeper into the blueberry nutrition literature next week and report back anything noteworthy.