Seems to be going around. Mine are not overly tall, about a foot, and are already setting buds. This is on dinnerplates too!
Bone meal will help the roots but try either alfalfa tea or perhaps Jobe's Tomato Food Spikes.

A gardening book, which has 'A-Z Gardening' in the title, states to apply bonemeal in June and early August. Hope that helps. [Don't have author/exact title of book at hand.]

I'd be happy if more of mine were as tall as 1-1.5 ft! Quite a few are, but I think we're right on target as far as early season growth goes here, and many are not even a foot tall yet. But before you know it, those stalks will be growing upward and the usual dahlia forest will evolve.

Info on bonemeal at the link. The only caution is that dogs seem drawn to it, so I'd keep possible digging in mind if you choose to use it. (I quit using it because of the dogs uprooting dahlias.) Tripleb's Tomato spikes idea worked great for me last year.

Here is a link that might be useful: Bonemeal info

my friend lives out of town a bit. when she breaks out the bonemeal the neighborhood dogs go nuts when they smell it. when she breaks out the bloodmeal, the feral cats pay her yard a visit. ugh.

Why is one not to use MG ? I use it, and have seen no problems.