H100i Fan Speed Issues

So, I recently purchased an H100i and 4 brand new SP120 PWM High Performance Edition Corsair fans. However, while trying to set up the new system, I've found that two of my fans will not go below ~1800 RPM. This is quite annoying as I'd much rather have a quieter system, but can't set the fans below their current speed, no matter what I try in Link.







Any ideas?