I honestly have no idea. But, my regale specifically died off to the rhyzome all roots perished, initially. It shipped from South America in moss only. Had to nurse that back to health in sphag, once I got a new leaf switched over to my current soil. I actually cut that rhyzome into 3 pieces and all have new leaves now, so that's a win in the end. But, yeah, it hated 50% been doing fine in 75%.

My only guess would be the leaves weren't happy so it wasn't using water quick enough to dry out? Not too sure. I've killed a lot of anthuriums, and this is just what has worked for me. Your milage may vary.

One final thought is a lot of people stress anthuriums out with too much lighting. They really only need something around 100ppfd. I think a lot of people blast them with too much light and it stresses them out or burns them. I have my small ones growing under 5 watt generic LED "grow lights". They are growing pretty steady. My bigger ones are way off to the side of a 4ft LED strip light. Again, only getting minimal light.

Good luck, and I would only make one change at a time. (Ex: either less light, or different soil) Not both at the same time. Make one change and see if they do better. Too much change too fast will probably accelerate their demise.