What kind of "BEGONIAS" are they? Is your bed in full sun all day? When you say bad, what exactly does that mean? Sunburned? Broken? What zone are you in and what kind of temps are you experiencing now?

Most begonias need some shade in the hot afternoon and never allowed to completely dry out.

They are the most typical ones that you get at the greenhouses, I cant think of the name of those at the moment. The leaves are just smallish, the over all plant is just not really growing. They are in early morning full sun until noon and then a large tree shades them for the rest of the day. They are growing in sandy soil, but have been using miracle grow about every two weeks. I have mulch down around them and recently been getting alot of rain, but normaly water them every other day. Like I said I have sandy soil and get really good drainage. Zone 6A

Wax begonias?

Make sure the soil is not real wet. I would take the mulch off if the soil stays wet and back off on watering.

If the soil dries out fast then you may have to increase watering or move them to another location.