A small amount of brown spotting just before your period, along with a cycle that's settled from 28 to 25 days, is a common pattern and usually not a cause for worry on its own.
Next Steps
Track it for another cycle or two to confirm the pattern holds. Weight is one of the common factors that can shorten or change a cycle, so it's worth mentioning at your next gynaecology visit.
Health Tips
See a doctor sooner if the spotting becomes heavier, lasts longer, or your periods stop altogether.