If you want to use non-consumable Cure spells after battle...

1: you shouldn't have used em during this battle

2: your element-lvl at the end of the battle have to be equal or even higher to your Cure-Element level...
in other words: if Serge's ele-lvl after a battle is on lvl.1, you're able to use Cure Spells you put into his lvl.1 grid (like Cure or Heal-1), but you're NOT able to use lvl.2 grid cure-spells (like Heal, RecoverAll etc...)

I hope you get what I'm talkin about...