That is a lot of rust for 9 months of use, although great that you are using the car.
If you were out over the winter, it may have been exacerbated by road salt. It would be worth having a look under the car too, to see if anywhere needs attention. There are hard to reach areas alongside the pedal boxes where muck gets in and if that’s mixed with salt, it can cause big problems.
It’s usually the areas exposed to grit and stones which lose some coating and then it starts to spread. If re-powder coating is not your plan, It’s possible to sand and spot treat areas with either Por15 or Simonez tough satin black paint, though it will look like a touch up job, unless you’re a dab hand. Better than rust though and if done in time, you only need small amounts.
As mentioned, once treated, rubbing down with anti-corrosion fluid like ACF50 will help prevent re-occurrence.