Need Help with Fans [nzxt s340]

Hey,

i Build my first pc and its working fine. But now to my Problem.

I have a nzxt s340 case with the 2 stock fans in back and top. I added 2 Front fans bequit Wing 2.

In bios i can controll the front fans, but the stock fans dont responded to Fans speed change. They always run on 1300 rpm, its rly loud...

How can i make them slower?

sry for my bad english