[sooxiwei]

oh, recall, ampullaria and mirabilis if not mistaken

for watering part, you should try clean tap water instead of planted tank water as it's full of fertilizer in it, plus some carbon dioxide...the leaf of nep takes in carbon dioxide when other requirements are met for photosynthesis but the roots takes oxygen, try to change the watering and see if it helps or not.

other factor could include medium need change...