@Rhia: The issue with Subsurface Scattering arises from the Redfilter node linked to your 'Surface'. Each RGB channel outputs a grayscale map derived from the original texture map. The intensity of the output varies with the selected RGB channel; the Red channel outputs a brighter map, while the Blue channel yields a darker one. The illustration below demonstrates this.

Connecting the Redfilter output to the Subsurface channel alters its value range from 0 to 1, according to the grayscale map. This results in excessively high values that can overwhelm your Scatter. To address this, disconnect the Redfilter node and lower the Subsurface value to an initial setting of 0.01. Then, adjust the Subsurface radius values to achieve a more varied scatter tint, as the current values may not provide the desired variability.