Hormones can be bastards. Among all the stuff they cause to women is a vaginal discharge. It is mostly caused by high concentration of Estrogen.
Should you be concerned?
As stated on Krenizdravo Website
Is it (the discharge) Normal?
Yellow discharge after the period does not always have to be a cause for concern, as it is not so unusual, especially if there are no accompanying symptoms. After the period, vaginal canal cleansing occurs naturally. Yellow discharge in that period is a sign that you are fertile and that ovulation is on the horizon.
And now, in case you wonder when your ovulation should happen:
Ovulation and Fertility Test
More about the female hormones can be found on netdoctor.