I was just wondering if you know what the black is (residue of something that had been deliberately applied or splashed on) or if that is part of the problem. It's hard to say without examining the actual plants. As I say, I don't think the brown is necessarily unusual with daylilies, and earwigs can contribute at least some of it by pooping all over the leaf bases. There's also possibly a fungal element, maybe the leaf streak fungus but that's speculation. Whatever, it doesn't seem to do much harm. If you had that brown at the soil line I'd be more concerned. Some daylilies do have scapes that pull out easily when they're done (I assume when they don't pull out easily you leave them alone, otherwise it can damage the crown?).
The only thing I can think of for the black is maybe sooty mold - do you have aphids on the daylilies? If you can get a sharp close-up of the problem areas it may help. It's not rust.
