This may help: https://www.hometalk.com/2295735/the-best-way-to-clean-grout-ever
I use hydrogen peroxide and a toothbrush. Pour/squirt/etc the peroxide onto the grout, let it sit for a bit and scrub with an old toothbrush and then wipe up with an old rag or towel.
Tilex, bleach, scrub. Seal once cleaned.
Hi R: Check these sites for some answers:
This is the shower cleaner that we use to help keep grout and tiles clean and minimize the mildew - it works on kitchen grout too. I've also included a great article about mold if it's gone that far. Hope this helps! Hugs, Holly
PS - We have a FREE eBook with recipes for all of my homemade and all-natural cleaners. You can download it here --> https://pinkfortitude.com/thank#GreenClean
Oxy Clean and a little water. Scrub with toothbrush. Seal once clean