Does anyone know what's wrong with this Begonia Rex?

[aliiisha]

Can anyone tell me what this disease might be and how to best combat it on a small plant? If it needs to be sprayed, will it survive the winter if I cut out the spots for the meantime until it is able to grow and thrive again? The plant is begonia rex escargot. Any advice appreciated!

https://i.postimg.cc/XYbjJpr9/IMG-3939.jpg

 

[Nasir]

Have you placed it in kitchen ? If yes then have you been using any chemicals to clean the window that have any chance of spraying on this plant?
How is the sunlight and temperature conditions.
Here is good video about this plant that explains how to take care of this plant. I hope this will help you.