All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
Dear sister, the matter is easy, Allaah willing. You are obligated to stop the prayer and all the acts forbidden to a woman in menses when you see your menses [blood monthly discharges], and when you see a sign of purity, which is becoming dry (i.e. when the place becomes clean) or when you have a white discharge, then in this case, you are obligated to perform Ghusl and pray as we clarified in Fatwa 100850.
Afterwards, if you have bleeding again that can be considered as menses, which is within the period of fifteen days which you mentioned in the question, then you should wait until it stops, and when it stops, you should perform Ghusl because it is menses, so you are obligated to perform Ghusl because of it.
As for the discharges that you see other than the bleeding, like the yellowish or brownish discharge or what you described as brown in color and the like, then it has the ruling of bleeding (menses) since it is during the period of the monthly discharges. So, you should consider this as menses as well, but if you see the yellowish or brownish discharge and the like after the monthly bleeding stops and after the expiry of the monthly period, then you should not worry about any of these, because the yellowish and brownish discharge at a time other than the time-period of your regular menses is a period of purity and not menses, as we clarified in Fatwa 83454.
Furthermore, you are not obligated to perform Ghusl for every prayer, but if you see bleeding again after it interrupted, then you are obligated to refrain from performing the prayer and the like, until the bleeding stops. If the bleeding stops, then you should perform Ghusl and pray as we clarified.
Besides, you should know that some scholars are of the view that if a woman sees that she became dry during the time-period of her monthly menses, she should not take the initiative to perform Ghusl; rather, she should wait for a day or half a day because blood usually comes and interrupts, and it is permissible to act according to this view if this is easier for you even though the other opinion (which is that you take the initiative to perform Ghusl as soon as you see that you have become pure) is more appropriate in order to be on the safe side.
We hope that the matter is now clear in the light of the above argumentation. For more benefit, please refer to Fataawa 108423, 98693, and 96052.
Allaah Knows best.