Key facts: 12 days post-LMP corresponds to the $\text{peri-ovulatory phase}$ (approximately day 12-14 of a 28-day cycle).
At this phase, rising oestrogen stimulates cervical glands to produce copious, clear, elastic mucus (spinnbarkeit). This is entirely $\textbf{physiological}$ and causes NO itching, odour, or dyspareunia.
Pathological discharge comparison:
- Candida: curdy white discharge + intense pruritus
- Trichomonas: frothy greenish discharge + itching + offensive odour
- Bacterial vaginosis: fishy-smelling greyish discharge (Clue cells on microscopy, positive Whiff test)
None of these features are present here. The absence of itching and the timing 12 days post-LMP confirm physiological origin.
\[\boxed{\text{Physiological discharge}}\]