If they hadn't been there before I'd have said the white spots are probably hail. Do all your daylilies have them? Have you sprayed with anything?
I don't think the grooves are from slugs but wouldn't rule them out and other pests may come out at night so it's worth looking. One thing that got my attention is towards the top of the middle of the first picture. There's a white line that slightly squiggles. Can you see anything under the leaf surface there, and are there any more lines like that?
