Assuming other causes of discharge have been ruled out such as infection or thrush, and there is no discomfort, then I wouldn't worry about it.
Changing levels of estrogen can alter both natural secretions and the vaginal microbiome and typically settles with consistent use.
If you are only using it once weekly this is more like repeatedly starting it from scratch rather than doing a loading course followed by regular maintenance.
A very hypoestrogenic mucosa actually absorbs more, like parched earth, than a healthy mucosa.
Additionally some of it could be residue from the pessary.
