[Goosegirl]

I have always potted-up my large-flowered begonia plug plants in those trays of module cells - 15 to a tray. I know that a few always bite the dust but this year there is quite a variation in size. Some have grown well for this time of year, but some are still quite small. This year I used John Innes No. 2 and earlier on gave them a feed with dilute Tomorite as a little boost. Why does this happen? 

[mumofstig]

The same thing has happened with my dahlia tubers, some growing well, some half-hearted and some no shows  GG.

I've put it down to either low quality compost or perhaps I've over-watered them, so they've rotted 

[mrs bouquet]

I have given up with dahlia, but have good success with begonias.   I am sure correct watering plays a good part, but dahlias, I get those wrong.  Will just buy a few bedding ones later.  Mrs Bouquet

[Goosegirl]

I kept an eye on their watering and used on of those water meters as well. Just wondering if it's the soil-based compost that was a bit too cold and wet down below.