Hey Bubbles, if the plant is starting to decline it might have exhausted the resources in the soil it has. The solution is to re-pot in a high mulch mix. Good luck. I have been collecting begonias since I arrived in Colombia, & I think my count is 3 wild collected, & 17 hybrids... I should take photos of all of them to post! With such a beautiful plant, I am sure you know to pot the plant at the same depth as before to avoid causing rot on the stem. Begonias are so finicky about staying wet...