Yellow sprouts from tuber

SteveM

I don't know if this is really a problem but it is something I've never seen before from new tuber growth. These are purchased tubers of Formby Alpine and both have the same pale-yellow growth as the one plant shown in photo. It looks like what I would expect to see from a plant that was very deficient in nitrogen and doesn't appear to be virus. My best guess is that, for some reason, the plants are not getting nitrogen from the mother tubers and will green up when the roots begin to grow and get nutrition from the soil. Can dahlias that are deficient in nitrogen (or other nutrients) produce tubers that may store well but do not have the stored nutrients for proper new sprout growth? Or, were both of these tubers taken from a plant that had a chartreuse foliage mutation (I don't think so)?
Anyone else ever see this and have theories?

Teddahlia

I have noticed that some yellow flowered dahlias have lighter, yellowish leaves. Maybe this white one has that trait or, more likely, it is an older variety and good stock is hard to find.