How to treat angel wing begonia brown spots?
If you're looking to treat brown spots, it's always a good idea to start by identifying the cause. It's likely that the plant is infected with fungus. I think the best thing you can do is remove the plant and provide it with conditions that are nice and airy with plenty of moisture. If you feel it needs a little extra help, I would suggest using a fungicide to help it improve.
It might be helpful to spray some anti-pest on the leaves or other parts of the plant that are affected by pests.