unusual period

Clara
Usually this is how my period works
Day 1: starts LATE at night and super light
Day 2: heavy (for me anyways)
Day 3: light/medium
Day 4: super light
May do LIGHT spotting for a day or 2. 
This time....
Day 1: started late at night
Day 2: medium/light
Day 3: definitely borderline light spotting. 
They are usually the same every single time. Any ideas on why this would change? I'm not stressed and nothing has really changed.