The plants are watered four times daily via an automatic hose timer + sprinkler. My usual mix includes cinder, orchidbark, perlite, and a pinch of coir, very airy and loose. From what I saw I don't believe it was caused by heat. I have definitely been seeing heat stress however, mostly growth tips and new leaves getting very floppy in the noon sun. The only place I use pure sphag is with my cuttings, it tends to become compacted and decay quickly. Generally the cuttings are replanted before this can happen. Surprisingly, all that died had started strong root and leaf growth, newly taken cuttings seemed less affected. I may need to investigate other medias for striking cuttings.
I too am debating whether to move the plants in for the storm. I think I will wait and see how badly it hits the Big Island and Maui before making the call tomorrow. My biggest fear would be debris falling atop them. The last time we had strong winds a loosely attached window screen above fell on them. Luckily it landed right between the benches and only scratched a few leaves. My wishes go out to you Christian and Mach (on Maui)! 12 hours to impact...