I can't say whether 3 hearts for 100 NG was a good deal or not, since we do not know yet how easily these things will be to obtain within the Nutaku version of the game. For all we know, they could only be available through NG/FG transactions at 1FG or 100NG a piece, with the current LC deal (I got one from there as well) being a temporary introduction. So yeah, I grabbed this deal, just in case.

Anyway, more important matter is: who to apply these hearts to.
1. Waifu, that's obvious, so Acacia got one.
2. Fritillaria. She's a keymember of the first squad in my Whale team, so it's only good if she gets better.
3. Cymbidium. Also a member of the first squad in my Whale team. Her 2x passive is also unreplacable, so, as a 5*, she definitely needs the boost to keep up
4. Southern Cross. She's with Acacia in my debuff-squad. Also the only girl with a bloomed form available who I actually use in my main unit, and her debuff is only shared with Gentian. Southern Cross is the way better unit of the two.
5. Hypericum. I really don't want to replace the most awesome ninja evah with a rainbow, so this counter-girl gets a buff to keep up with the 6*'s
6. I had one squad left in my main unit that didn't have a girl with 2nd affection unlocked, so last heart went to Alpinia. I'm sure she'll benefit from it.