Akerne Rain Mix?

[Ray]

I agree with Orchidtinkerer on that. Sometimes if newly-growing root tips com into contact with a very dry substrate, the tips become desiccated like that.

What is that potting medium? It's looks more like mulch than bark that has been treated for use as an orchid medium, and if that's the case, that, alone, could be the issue. Orchid bark is usually aged or steamed to extract resins. Not so with mulch, and it is those resins that might be the problem.