Answer: If all of your plants are receiving the same amount of water and sunshine, I don't think the cause is from that. However, the site with the ailing Mugo may not be draining as quickly as the other sites. Why not dig down 3-4" and see how wet or dry the soil is and then compare it to the soil around the healthy plants.
Aside from soil drainage, your mugo may just need to adjust to it's new home.
Best wishes with your garden.
Q&A Library Searching Tips