May be normal but also no reason to not get it checked out. Or at least mention at your next regular doctor appointment. Kidney disease is not binary and has phases, you might be getting an early warning sign with your sweat. You might just need to hydrate more as you sweat more.

I worked in the kidney industry for a bit after the hospital thing and it’s something you don’t want to mess with. You can significantly delay the need for transplant if you catch it early.