As you have never had this type of spotting earlier, you should suspect an implantation
bleed, which can happen a little prior to the onset of the normal menstrual cycle. Ovulation bleed cannot happen at this time as you have 25-day cycles, which means you usually ovulate on the 10th or 11th day. Please wait for the onset of your next normal period if it is a minimal spotting; else, see a specialist for further appraisal of the situation. You can get an assessment of the serum beta-hCG
titres after a couple of days to confirm/exclude pregnancy
. Hope this helps.