Filters and wipers yourself, let the garage do the fluids.

Either the battery is failing or you have a parasitic draw.

So from experience, Kia’s will sometimes keep the visor mirror light on after you shut the engine off even if you put the visor up. You need to close the little door on the mirror, to shut off the light then put the visor back up. The little light on will draw on your battery overnight.

Not saying that’s what’s going on but just as an example of the odd little things that can lead to a power draw without you even thinking about it. Turning the car off doesn’t always mean that everything inside also turns off.

Try unplugging all of the usb stuff and make sure all the lights are set to off and see if you’re still getting a lower voltage.