Wilted dalias, how do I help them?

Last year I started growing dalias, and my dad replanted the bulbs this season. He replanted all of the bulbs together (which I know, not a good idea), and then the leaves had a weird texture and a lot of them were dying. I thought maybe all the plants weren't getting enough nutrients so I transplanted some of the bulbs into another pot, and then immediately both plants wilted, with half of the stalks just dying. The stalks feel empty, there's white stuff (mold?) growing on the parts we cut that were dead dead, the leaves still have a weird texture, and the flower buds are all turning brown.

We thought first it was overwatering, and then shock, and now we just don't know what. Does anyone have any ideas/how to help them? Any advice is welcome!