Sometimes, the fans may come loose on the bearing, the best thing to try is removing the fan gear from it's housing and pop it back in.

Check which fan is making the noise by pausing them, press on their center so the fan stops spinning, if the noise stops then you have found the culprit fan.

 After you have reseated the fan gear, if the noise is still present then you might need a fan replacement. Below is a video on how to reseat the fan gear. 

Also, make sure to check the fan power cables, please be sure they have not come loose or are disconnected, it may resolve issues where the fans are not responding or aren't moving.