Spotting week before period

I (18F) have been getting my periods since I was 11 and they’ve been pretty consistent.
However, since the last 4-6 months I’ve been spotting 7-10 days leading up to my period. This blood is red and fresh. I have no other symptoms that I would get with my period.
After the spotting, I get my usual period on the date it is supposed to come, and it’s the same as it has always been (no heavy bleeding etc)
I am also not sexually active.

I’m guessing it’s due to low progesterone levels or vitamin D deficiency.

Just wondering if other women also have this issue, and what the doctor had to say abt this.