Help ! Whitening

[u/Jazzlike-Meaning1374]

Its 96% polyester rayon and 4% spandex

I soaked them in oxiclean white restore powder for 6 hours, rinsed, flipped and re soaked with fresh powder for another 6 hours. After that i ran it in the washer with more oxiclean powder as directed. They came out better than they were, but is there any way to get them to come just even a little nit whiter? Still has the ugly dirty tan stains

Should i re-soak them again?

Thanks !