Or is it heavy bleeding, unusual in quantity, or stained with greenish mucus
, or anything which could signal an infection? Is she showing any signs at all of being unwell? (Lethargy, shivering, drinking more water than normal, vomiting, off food?) Those could all be signs of Pyometra, but even if she doesn't have those symptoms, she could still have some infection. Pyometra most commonly occurs a few weeks after the heat cycle, BUT it can actually occur ANYTIME.