I posted this in questions yesterday and didn't get a response. Not trying to be pushy, but it seems like many questions get asked and some can sometimes fall through the cracks. Plus, it seems like it's fairly active in this forum with a lot of knowledge

I have two Snow-in-Summer (Cerastium tomentosum) plantings within 2 feet of each other and as you can see in the picture, their health seems to be quite different. Any thoughts on this?

Of the few notable differences that I know of, the one on the right may get more water funneled to it by the way the landscaping runs. The one on the left gets slightly longer morning shade from the barrel half that it is planted next to. However, I would say that both get "full sun" overall with some late afternoon shade.

I've never grown this plant and can't offer much, although I have had this happen inexplicably with other plants growing side by side. I often wonder if one simply started out weaker somehow. If they were originally grown from seed perhaps some recessive gene showed up, something that makes it susceptible to weakness or disease. If they're propagated by cuttings or some other form of cloning, it's even more mysterious.

Gocart, I don't grow it either. Neal has some good points. Sometimes stuff happens that we have no control over and plants don't do well. I am wondering if there is any leaching from the barrel into the nearby soil that maybe toxic to the roots. My suggestion at this point is to try and move it to see if it will recover before it get worst. Keep us posted on the outcome.

Interesting points, Neal and Mike.

Also, how about the possible influence of more watering to the plant on the right?

Alpines, like snow-in-summer, need good drainage for optimal growth, but good drainage is also associated with the need for additional watering during hot summers. Have seen both points noted for snow-in-summer in gardens.