It’s always a tough call when things start to turn black and crispy, but in my experience (18 years total in ‘The Biz’ and my Master Gardener schooling) it’s usually too much moisture suffocating the roots.
No roots, no plant! ;)
Hope you can correct the situation. I love Brunera and plan to add some in the future when I get ambitious about a perennial shade area.
Do you think the hot sun we have had these past few weeks, late in the morning and early afternoon, could have “cooked” the Brunera? The two that are okay so far don’t get quite as much sun.