Ask-a-Dave's-Gardener: Bottle Gentian not Doing Well, 2 by Chillybean

Chillybean wrote:
I am posting this over here since there seems to be no activity in the Disease forum:

We planted three Bottle Gentian (Gentiana andrewsii) dormant bare roots last fall. We are in Central Iowa. They all have received about the same watering. and have come up, but one looks rather ill: stunted growth, lighter green and spotty.

I\'ve seen a type of mildew on some of my native plants in other areas, but that usually shows up later in the season, so it doesn\'t effect the growth or flowering too much.

The first image is one of the healthy plants and the other is my sick one. This is in one of my dryer areas and on the south side of the house. Does anyone know what the trouble might be?

Thank you for any help.