Brown spotting before period

[merle]

I know brown/dark spotting before the period starts is common and represents old endometrial lining coming out, but does it occur in an optimal, healthy cycle? My periods have been improving in terms of pain as I've made various health changes thanks to the Period Repair Manual, but I am now getting this brown spotting whereas before I only got it at the end of the period. I'm wondering why my body is hanging onto old endometrial lining.

ETA: This only happens for about one (max two) days preceding my period.

[Emma s34]

This can be a sign of low progesterone, this happens to me too. It only started happening after I took progestin based birth control for two years. Unfortunately my periods never went back to normal after that.