Luckily I took its photo during noon time, it was gone in the evening when I try to find it again because it has been removed by my mother who also loves gardening.
Days later, I found the other leaves which were also dotted.
I am not sure if it is unhealthy or it is just the life cycle of a water lily leaf. Hope more leaves will grow soon and bloom beautifully.
If we keep our body healthy, sickness is not part of our life cycle.