In my bathroom I put a new floor with porcelain tiles. I grouted it and sealed the grout with two layers of water-based penetrating sealer. The sealer left white taint on the grout and tiles in few spots on the floor.
Try a nylon backed sponge and a liquid cleaner. Before moving to a powdered abrasive cleaner, I 'd test it on some scrap tile first.
Porcelain tile is pretty impervious, but it doesn't hurt to be cautious.
Use a stiff bristle brush on the grout.
"They that can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety."
B. Franklin 1759
what was the water base product? was the grout cured? how long did you wait between coats? milky white areas could be moisture intrapment. if this is moisture entrapment, hot air from a hair dryer may help speed up evaporation or test a small area with alcohol or nail polish remover(acetone) to open the sealer and allow the moisture to evaporate out.