Here is the description of successfully growing your C. mossiae from an expert A. A. Chadwick.
Cattleya mossiae
If it were mine growing in the sphag, I would do as Ray says plus I would add additional holes to the sides of the pot, increase the light as much as possible and also the air circulation in the grow area.
You have a beautiful catt that will reward you with beautiful blooms in the future. Good luck.
Brooke