بسم الله الرحمن الرحيم
(Fatwa: 744/618/B=05/1435)
The maximum period of nifas is forty days while it has no minimum time. If the blood comes after forty days it shall be counted as istihaza and salah is not exempted in the state of istihaza. In the question mentioned above the starting ten days are of nifas. And the next month in which no blood was experienced you will have to make up the missed salah of this period along with witr salah. And then the blood which came in the last month if that woman does not have any fixed habit then by deducting the habit days the salah of rest days shall be made qaza along with witr. And if there is no fixed habit of menses then she shall offer all those salah along witr excluding the ten days.
Allah knows Best!
Darul Ifta,
Darul Uloom Deoband