It seems unlikely that there is some soil difference in rows so close to one another but is it possible there's some unseen physical soil factor affecting the rows, like moisture or fertility or acidity?
I'd hate to worry you about major issues like botrytis but is is it possible you got infected seed garlic?

I can't see it being the soil, it's been worked for 10+ years and the seed stock is from the same source so I imagine if the Rocambole was infected the Porcelain would be as well. The contrast between the two is shocking. The Porcelain is picture perfect. Some of stalks as thick as my thumb already. Is it possible this could be a climate/acclimation issue? I'm about 40 miles north of the seed source, but at least 1000 ft higher in elevation (it did snow her two nites ago and it's in the lower 30s right now, but that's not really uncommon).

Might try hitting them with a bit of Nitrogen (Urea type lawn fertilizer works well). Garlic loves Nitrogen at this stage, and perhaps the Rocamboles are more sensitive.

My Rocamboles (German Red, Killarney Red, Spanish Roja, and Russian Red) and my Porcelains (German White) are equal and beautiful and richly green.

TomNJ