58C is a pretty high idle temperature for that Noctua cooler. It doesn't leave very much overhead for full load CPU work(rendering). If your cooler is installed properly, you may have an issue with air-flow or thermal stacking. Are your GPUs porting air directly into your case or out the back?
Turns out it was an air flow, fitted two more 140 mm fans to the side of the case and the temp has dropped a lot. Thanks for your advice