Spotting for first time whilst on pill after over a year of use.?

I've been on Microgynon for over a year now and have always taken my pills correctly, the same time each day give or take a couple of hours. My last withdrawal bleed arrived on time on the 31st Oct and lasted the normal 3 or 4 days, but last week on the 11th Nov I got some light spotting blood that was brown/pinkish. I've not had spotting in the whole time I've taken the pill, and heard that it's normal right at the start but presumably not after a year? This light spotting only really finished on Monday/Tuesday so was going on for a good 4 or 5 days, and I'm quite confused by it to be honest. I will finish my current pack next Wednesday 24th and my withdrawal bleed should arrive on the 28th as it always comes the following Sunday... but has anyone else had spotting like this between bleeds after using the pill for this length of time?