Brown CM? Advice needed please x

It’s day 13 of menstrual cycle so this morning I tested Ovulation and got a flashing smiley - high fertility today! 🎉

BUT!

Just been to the loo this evening and I’ve got a brown and clear discharge - what could this be? Only even known of clear eggy CM.

It was almost like the tail end of a period but a lot lighter.

Thanks ladies xx