My guess is that caterpillars got them. They love dill. Also cilantro and parsley. They will go wherever any one of these are.
I had them last year...they look bright green with dark backs. Eating my cilantro and parsley. I saw them earlier this year, but sprayed as soon as I squashed a couple of them, and haven't had a problem since.

Possible, though they haven't touched the parsley.

Still amazed at an entire plant gone overnight.

It's the caterpillar of black swallowtail - a beautiful butterfly but the larvae are steady feeders on dill, fennel,parsley, carrot and related plants. If you can spare a little patch of one of these for them somewhere, you can handpick them off the plants you want to save.

They will also eat the weedy Queen's Annes Lace (wild carrot), so if you have some of that growing nearby you can move them there. I rarely see them on it naturally - maybe the plants are too isolated - but once on, they seem to feed on them readily.

Hanpicking means you have to check almost every day because these caterpillars grow very quickly if you don't keep after them.