Michelle, even though you are in a warm zone, I think these begonias simply need a period of dormancy and perhaps thrive best when kept in humid eniironment with filtered light.

I dunno... fo sho, so check for better expert begonia advice than me, but my begonias tend to want SLEEP during this time of year. When I lived in sunny Southern Calif my begonias lasted all year but now I am in zone 5b and have to keep the roots warm to even save one.

I sure do understand your panic however, since I've nursed plants that were starts from my Grandmas's plants and she was born in 1898. Wish I could tell you EXACTLY what to do, but begonias like an Angel Wing (for me) tend to simply need a few months of sleep. I hope yours will soon bounce back.

Another option is to soon as possible propogate that special plant with divisions or cuttings under lights and suddenly have several plants that will be clones. Ever WHAT... I sure hope you can save that treasure that is now yours to keep alive. Just don't assume the plant is dead when it's only asleep. My wife once made that mistake with me.

jim