My suggestions:
Adaline: I usually prefer Adeline, but I have a feeling you'd like the nickname Ada.
Alice: almost unbelievably pretty.
Amalthea: it's a bit much, but I love it so much, and Thea is very chic.
Astoria: over-elaborate, but starry, and fits in well with names like Daphne or Penelope.
Calliope: my favourite muse name. So underrated, but Callie does it a disservice.
Charlotte: sooo basic, but it reminds me of apples, so perhaps there's a tie with nature? And Lottie's cute.
Clio: I prefer Cleo, but Clio fits in better with your fondness of mythological names.
Coraline: fantastic book and film, and Cora makes a nice NN.
Evening: nicknamed Evie? Far from my usual style, but I'm liking it today.
Hazel: one of these names I liked before it was cool. So warm and autumnal.
Iris: it used to be one of my favourite names. Ticks off the natural and mythological boxes.
Ivy: so beautiful and inky that I don't mind its popularity.
Lark: if one is not tempted to go so far as Nightingale, Lark has nice connotations. Les Mis?
Lily: boring, but so pretty, and works with Henry.
Magdala: cool Agatha Christie association. Magdalen(e) and Magdalena could work too. Or Maud(e), if you're feeling bold.
Magnolia: NMS as I dislike Maggie, but how about Nola?
Margaret: I'm not too fond of it, but Peggy, Daisy, and even Pearl could work as nicknames, and it's just as buttoned-up as Henry.
Mary: I'm in the minority here, but I don't find it stale. It's no-nonsense, but warm and welcoming and earthy, and Polly deserves a comeback as a NN.
Rose: or Rosalind, Rosamund, Rosemary, Rosalie, etc.
Saoirse: too Irish and too Ronan? It sounds like a bubbling creek.
Violet: very common, but it's charming, timeless, and intelligent.
Zinnia: I'd love to see more of her! So fun and zippy.
Marigold should be given to as many children as possible. It's beautiful and shimmering and golden and reminds me of sun showers and meadows.
I like Poppy, but I'd let her go. Apparently it means grandfather in US English, and it kind of feels like a cat's name.
Prairie is what I'd name a wild stallion in your typical coming of age horse girl movie.
Myrtle is fun in its clunkiness, but I wouldn't bestow it upon a child.
Maple makes my teeth hurt.
Pommeline is a bit out there, but it's nice, reminds me of jam. I like Pomona too.
Ione always sounded somber and sad to me.
Xanthe is fun. Xanthia looks like a medicinal drug.
Ianthe is too light and fluttery, she'll fly off.
Dot com. I prefer Dolly.
Pippa is dangerously close to Polish slang for female genitalia.
From your list, I really like Juniper, Wren, Marigold, Annika, Daphne, Matilda, and Zelda.
masculine list:
https://www.behindthename.com/pnl/191050/124079feminine list:
https://www.behindthename.com/pnl/191050/124080