It’s hard to pinpoint exactly why painted leaf begonias start to wilt, as there could be multiple reasons. First, I suggest checking out your plant for any obvious signs of a pest infestation. If your plant is clear of pests, here are other suggestions as to why your plant is wilting. 1. Soil is too dry or too moist 2. The soil needs more drainage - in this case, work in a little perlite to your potting mix. Also make sure your pot has a drainage hole. 3. The plant requires more light (though make sure to keep it indirect) 4. The humidity levels needs to be increased.