So! In my desperate attempt to make the grout lines white again (I know... its our own fault for getting white grout), I jumped in my car and drove to Canadian Tire to buy a Clorox Bleach Pen!
Boy did this work! I got the idea from this blog here, and thought it was brilliant! It took longer than I expected for the bleach to work, but when it did, my grout lines became sparkly white and I barely had to do any work!
I put the bleach on the lines that needed the most work, and then when it was clean, I washed the floor with HOT water to make sure to remove any leftover bleach that was on the tile. If you have tough stains on your grout I highly recommend this method. I know cleaning with bleach is "a big no-no", but this worked for me!
If you have other ideas to clean grout, let me know! I would also love to hear ideas that are natural as well!