Hi Xuan,
Is the violet you are showing us a named and registerted violet? I ask this because many violets are put out on the market without names becauses they are unstable and tend to sport. I suspect that your plant may be one of them.
Fred in NJ

Hi Fred, thanks for responding. Most of my AVs are NOIDs and so is this one. So you call it "sport"? Is there anyway to prevent AVs from getting sport?

Xuan

Xuan,
A "sport" is a genetic change or mutation. Sport can also refer to a plant that has changed in this way. The only way I know to prevent it is to get named varieties that are reputed not to sport.
Adam in NH

Thank you, Adam, I understand it now. Since it's impossible for me to get named varieties in here, I don't mind "sport" so much as long as the plant is healthy.

Xuan

If the plant has sported to solid it will likely never show the white again.

The difference in your growing conditions in the two locations could be humidity. You might try adding a lot of humidity to your present location but this will not change the mutated plant.

Nancy