All perfect praise be to Allah, the Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
You have to make up for the days of fasting that you have missed. There is no expiation due on you. Please be informed that the yellowish discharge that is connected with the menstrual period is part of the menses. However, such yellowish discharge is not part of the menses if it appears outside the period or after the period has certainly expired.
If you saw the yellowish discharge during your period, then it must be menses. That you broke your fast because of this is what you must always do. If you saw such yellowish discharge outside the days of your menses and you broke your fast that day, then you would only be required to make up for the fast. This is the view of the majority of the Muslim scholars who do not regard the expiation as obligatory except for the case of breaking the fast by having sexual intercourse. According to the Maliki scholars, the expiation is due for breaking the fast, even if due to other than sexual intercourse, provided that the respective person does not have an acceptable interpretation to justify his fast-breaking.
In your case, you are only required to make up for the fast that you have missed since you already have an interpretation that is most likely to be accepted for breaking your fast; in addition, you were not aware of the ruling.
We would like to tell you that if you have to provide the expiation, then you should consider 60 poor people for that, and not only one person.
We would also like to state that you do not have to fast a day extra to the days that you have missed, even for the sake of assurance. Rather, if your period expires, then you perform ghusl (ritual bath) and observe the acts of worship like prayer and fasting. After Ramadan, you are required to make up for the days that you have missed only. In contrast, if your period is still on and you have not recognized your purification, then you should not abstain from food and drink. Rather you must break your fast as long as you are menstruating.
Allah knows best.