The pedal should not "go to the floor" at any time. There should come a point in the pedal travel where it no longer moves down. In other words, it should become firm.
If your pedal is "getting soft" and allowing travel to the floor you have a very dangerous condition that needs immediate attention.
I'm NOT a believer in coincidence and your recent "rotors, pads, and brake fluid" service is, for me at least, the source of your problems. Either that was done incorrectly or there are other brake system issues that were not addressed.
- Check that the brake pads, rotors, and other parts changes are appropriate for your model.
- Verify that all parts are properly installed.
- Verify that the brake system is properly and fully bled. In some models, and yours may be one, the ABS pump needs to be activated by the service diagnostic system to fully bleed the lines. Some shops may not have this equipment for your Subaru.
- Check that there is not a vacuum leak in the supply to the brake booster.
- Check that you don't have a "soft" brake line.
If you cannot do these things yourself, then take it to a reputable shop.