Are temp problems a new issue? Are these while under load, and if so are we talking typical gaming or some sort of productivity task?
We're in the middle of a heatwave so higher temps aren't unusual, and other factors such as your case cooling and room temperatures etc are going to play a part too.
I'd not bother with Asus software personally, see what MSI Afterburner states but I doubt it'll be much different.
Regardless, the cards simply run hot at times, they're pumping 575W through them so honestly those temps aren't unusual for the card.
The ASUS GeForce RTX 5090 Astral is the company's $2800 flagship RTX 5090 model. It comes with a massive quad-slot, quad-fan cooling solution that weighs over 3 kilograms! Thanks to the large factory overclock it can deliver additional performance and temperatures are very low.
www.techpowerup.com
You could consider an undervolt, I've never come across a 5090 that wont work perfectly fine when power limited to 450W.