So I just noticed that my top 200mm fan was loud. Kind of a lower pitched rumble noise when on high. on low speed, the sound wasn't too bad.
I tried resting the top fan on top of rubber washers, and it was still loud.
However, if I lift up the fan slightly, once I get about 2 inches above the case, the noise drops down dramatically once it's bringing in free air.
I'm wondering if the fan is dying, or if it's something about mounting it on the top of the case?
(What I have not done yet is tried mounting a different 200m fan on top, either buying a new one or relocating one from the front. To be honest, I don't think I really need the extra cooling at the moment and I was in a hurry to get the system back up)