Oo, yan ay common talaga, especially pag first few days ng period mo or towards the end, it's just older blood na oxidized na, kaya brown instead of bright red. But kung persistent siya for days or may strange smell or accompanied ng cramps na sobrang sakit, best check with your OB para sure lang, kasi a few of us moms na-worry din before and it turned out okay pero mas peaceful ng mind pag na-confirm ng doctor, di ba?