1. If you suspect any issues with the soil condition, try to grow some in containers with external soil source; apply phosporous (bonemeal or other sources) to ensure healthy flower growth.
2. If you suspect the quality of the planting material is the issue, try new sources next year.
3. Ensure adequate sunlight (this was one of my biggest learnings this year!) for the plants.
4. Watch out for bugs (I don't think that is your major issue here).

My 2 cents.

Dfever

The potting soil was Bacto brand. These tubers I planted last year and they survived the winter, the soil didn't change at all except I added more on top of it .

Should I wait for dormancy and dig them up?

Everyone's told me dahlias don't overwinter in the ground, but mine all came back, and we even had "Icemageddon 2014" down here.

True that. Although I do confess that all of mine are Home Depot varieties and perform beautifully.

They're common, sure, but still very pretty. Just because it's common doesn't mean it can't be a great plant that's a joy in your garden.

I'd be more worried about Wal-Mart's cut-rate policies on goods. Ten to one the nursery isn't the best and it's more than likely they don't trim out virus-infected tubers.

Ted had recommended a 'dahlia nursery,' which specializes in dahlias and make it their business (literally) to sell good stock. The nursery down the road that sells whatever is in season most likely buys dutch varieties in a large batch, and starts them in pots to sell to you.

Here is a list of US dahlia nurseries, most of which are reputable... But buyer beware, as in all things.

If this has been happening two years in a row, I would find a fungicide that you can use as a drench, and water each plant thoroughly up to a foot around the stem as soon as you can... Personally, I'd do it again right after frost and in the spring to try to knock out the problem. That might be overkill, though.

Good luck!

I still don't trust Wal-Mart just on general principles. :)

But I take your point.

>>The mis-labeling is my biggest complaint. And this even goes further in that they are now selling packages of several varieties with no indication as to the names of the varieties.

Agreed. While packaging mistakes do happen, they shouldn't be common. So far, my Home Depot purchases have all contained the exact cultivar listed on the package. They've even contained more viable tubers than the package claimed in the case of higher volume packs--although the one or two tuber packs usually do contain exactly one or two tubers.

So far, I have no complaints. They're not going to be unusual dahlia, but for most of my beds, I'm not looking for anything particularly unusual. A central plant of moderate interest is what's called for to avoid yanking attention away from the rest of the design and diverting too much interest away from other, less flashy, species.