Use a product with bleach in it: Clorox Cream Bleach Cleanser; bleach and baking soda as a paste; pure bleach (use a mask); bleach and water and Dawn. Use your choice of solution and clean the entire floor, focusing on the caulk. Rinse and dry the floor, and wait another day to be sure. One good sealer would be a water-based floor sealer, but of course there are oil-based sealers, varnishes, and wax sealers, and others. Best wishes on your project. 😊
Here are some links for you to check into. There are some great tips available!!!
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. Hope this helps! Hugs, Holly
PS - I'm getting ready to release a FREE eBook with recipes for all of my homemade and all-natural cleaners. If you want to know when it's released, you can get it here --> https://pinkfortitude.com/thank/