They're probably being kept too warm. They really need frost free....an unheated greenhouse or a shed.

As for the growth, i'd remove it personally.

I d move them slowly to an unheated frost free place. cool bedroom first then porch then shed. over a few weeks. as for the growth I wouldn't worry about it.

If it's dahlias that are shooting "long and straggly" don't panic. March time, not before, you cut off the shoots just above where they join the tuber, as if you were taking a cutting. From that point, they will produce fresh shoots.
Until then, just put them somewhere as cold as possible above freezing.

Thanks to all of you for your feedback