Yes! After repotted my Ness Fantasy Gold to a smaller container for about six weeks, I have finally found a sign of life! My plant is finally growing! This has confirmed that my guess is right. Not only did I overwater my African violet, the ridiculously huge pot probably had caused rotten roots in the plant. Lucky that I have taken the correct action early enough, else my plant would have been killed by my silly ignorance (again…).
While a smaller container is the major factor that brings life back to my plant, the weather now in Hong Kong probably helps much as well.
It seems like everything just grows in spring 
