Kushaq brake discs rusting overnight in rain + grinding noise for a long time — anyone else?

I live in a place with frequent rain and high humidity, and I’ve noticed that the brake discs on my Škoda Kushaq develop a visible layer of rust overnight, especially after the car has been parked in the rain.
I understand that some surface rust on brake discs is normal and usually clears after a few brake applications. However, in my case, there is a noticeable grinding/scraping noise while braking, and it sometimes continues for quite a while instead of disappearing immediately.
Has anyone else experienced this with their Kushaq? Did it turn out to be just surface rust, or was there an issue with the brake pads, discs, calipers, or something else?
Also, if you got it checked at the service centre, what was the diagnosis and fix? Would appreciate hearing from owners who have faced something similar.