Irish mosses are inconsistent – Reddit Post

Hello r/gardening. I was hoping to get some advice on why my Irish mosses are growing to inconsistently. I planted them in July of this year and it seems that the second batch I planted are doing considerably better. As you can see for the picture they are much more green and full. The plants on the left seem half dead and stringy. This has been the case for the last 2 months. Everything seems to keep living but they are considerably different looking.

I live in the PNW. Any advice or context would be great.