Hello, I've not grown tuberous begonias, only a long lived angel wing, which lived on a covered porch in the summer and a pot of the bedding wax begonias which I also overwinter.

I was able to get a dozen corms of non-stop and other "hanging basket" tuberous begonias on clearance this spring; they were solid and healthy looking and sprouted when I potted them up.

However, about half have rotted! Could it be that being on the uncovered patio, part shade, with all the rain we have had was too wet for them? I potted them in a mix of compost and peat with extended release fertilizer -- wrong? Should I repot them into a sterile commercial mix?

I want to save the remaining plants (some look fine, others seem to be struggling) so any advice would be appreciated!