Begonia erythrophylla: spots on leaves?

Hi, am looking for help identifying what is causing the spots on some of the leaves of my begonia erythrophylla and if there is anything I can do to save the plant. Photos attached. Thank you!

 

Does it get a lot of sun? Water on the leaves when they're in the sun could cause sunscald.

 

It's near a northeast facing window, so, a little sun in the morning but not much.