I planted three Delphinium 'Summer Nights' plants a couple of weeks ago, and two of them are looking ok, though not really a lot of blooms, but the third plant is looking very thin and unhealthy. I have been making sure they get plenty of water. They are in a full sun location. I know the soil looks poor in this picture....it was a grassy/weed area that just got tilled for the first time last year. I have mixed in compost and top soil last year and this year....the soil is very loose, and doesn't seem too bad despite how dry it looks on the surface. Any thoughts? Thanks.