بسم الله الرحمن الرحيم
If the effect of the impurity was removed from the clothes when you washed them, they became pure. And if the effect of the impurity remained, then in case of mixing other clothes, they (other clothes) shall turn impure only when the first clothes are wet to an extent that when they are squeezed water drops from it and when the other clothes mix with them they become wet to an extent that lets some water drop from them on squeezing. But if it is not so then the other clothes shall not become impure. It is not necessary to reoffer the salahs which were offered in those clothes:
قال فى الهندية : إن لف الثوب النجس فى الثوب الطاهر والنجس رطب فظهرت نداوته فى الثوب الطاهر لكن لم يصر رطباً بحيث لو عسر يسيل منه شيئ ولا يتقاطر فالأصح أنه لا يصير نجساً (1/102 ط اتحاد)
Allah knows Best!
Darul Uloom Deoband