What causes your blood to be brown when it comes out at the end of your period?

Im 38 and have this problem now for awhile. my period last 4 days but by the 6 to 7 th day from starting i have brwon bleeding or spotting . could it be from a blood clotting during my period?What causes your blood to be brown when it comes out at the end of your period?
Simply because this is "dead" blood... the red blood cells which give fresh blood it's bright color have died as the tissue sloughs off of the uterus. This is normal and just the final portion of your period.
age
You'll find that "new" blood is bright red and older blood is a darker colour..
every once in a while that wil happen your period may be developing newer days
It is more or likely just older blood that is coming out. I have had this in the past and was told it was nothing to worry about. Sometimes our body doesn't get rid of everything right away until the next month. When this happens it comes out with a brownish color to it.
Well is not a "age" problem, its a oxidation process, it like an apple one you cut it is white after 5 minutes it start getting darker as it gets more contact with oxygen. It is normal
Minor blood clotting during periods is normal. Menstural blood is not "pure blood". It contains other waste products generated after the ovum degenerates, they give a brownish hue.