Interesting article:

The plot of planetary distance & mass for this star shows an increase of planet mass closer to the star in the interior system inboard of the 5 Jupiter mass gas giant formed @ the snowline.

This plot is the most important part of the composition reportage for this system as it indicates that the interior of the system is an accretion based planetary series which formed before the star switched ON.

The main driver therefore for estimating composition in that case is the composition of the nebula that the star condensed from. As such the star's C-O ratio is unimportant and the C-H and O-H ratio of the nebula (particularly the central star) is the key. It is likely that the interior planets grew into gas giants from tidal ring planetismals, and variations in the C & O ratio of the interior planets are likely an evolutionary feature of insolation on the planets since their formation which will govern the loss of H & He in particular from the upper atmosphere.

As the star is quite young, there is likely to be a lot of methane & water and currently few diamonds (unless you look @ impact debris) is in the upper atmosphere of the nightside.

have a nice day: Ag